Effects of field-oxide volume ratio and interface-charge density on submicron modified-locos isolations

Abstract

The effectiveness of submicron modified-LOCOS isolations as functions of field oxide volume ratio and field oxide interface state density has been studied using 2-D device simulation. Both the field threshold voltage and subthreshold gate swing of the parasitic field transistor increase as the field oxide volume ratio increases. This is a result of the reduced drain-induced-barrier-lowering and the fringing-field effect at the field oxide corner. Although a higher field oxide volume ratio provides improved isolation, the surface states generated during the field recess process have to be minimized to avoid their adverse effects on submicron device isolation.