Investigation and Modeling of Mixed Halogen Freon/Oxygen Plasma Chemistries for Tungsten Etching

Abstract

Chlorofluorocarbon/oxygen reactive‐ion etch (RIE) chemistries for tungsten etching exhibit a thermal etch rate independence not associated with . Substitution of for in the system has led to the discovery that the role of the chlorofluorocarbon is essentially one of atomic Cl generation. Etch rate and optical emission spectral data obtained from plasma and RIE‐mode etching, from selective loading experiments, and from variation of the macroscopic process control parameters for the chlorofluorocarbon/oxygen systems, have led to the formulation of a hypothetical reaction pathway involving neutrals. By the proposed mechanism, atomic Cl is thought to be indirectly responsible for improving the contact efficiency between the plasma and metallic tungsten. Etch rate models based upon this hypothesis are shown to agree well with actual data.