Finite-length mask effects in the isolation oxidation of silicon

Author to whom all correspondence should be addressed A moving-boundary problem modelling the two-dimensional isolationoxidation of silicon is analysed in the limit of reaction-controlledoxidation for a finite-length nitride mask. Encroachment underthe mask caused by silicon oxidation then occurs from both sidesto produce two ‘bird's beaks’, and it is the interactionbetween these beaks on which attention is focused. This effect,termed ‘bird's beak punchthrough’, is currentlyof interest in submicron silicon-isolation technologies.