Medium energy ion scattering analysis of reactive ion etched Si(001) surfaces

Silicon surfaces reactive ion etched in CF4/H2 plasmas have been examined using medium energy ion scattering and core level photoemission. Surfaces analyzed in ultrahigh vacuum have a significantly higher fluorine content than surfaces that have been exposed to air prior to analysis. In addition, an unusually large cross section exists for ion beam desorption of some, but not all, of the fluorine. Based on core level shifts, we demonstrate that fluorine desorption arises from both the fluorocarbon film and the underlying fluorosilyl layer