Finite-length mask effects in the isolation oxidation of silicon

Abstract

A moving-boundary problem modelling the two-dimensional isolation oxidation of silicon is analysed in the limit of reaction-controlled oxidation for a finite-length nitride mask. Encroachment under the mask caused by silicon oxidation then occurs from both sides to produce two 'bird's beaks', and it is the interaction between these beaks on which attention is focused. This effect, termed 'bird's beak punchthrough', is currently of interest in submicron silicon-isolation technologies.