Method of forming a reduced size contact in a dielectric layer by using bird's beak of oxidized polysilicon to create an etching mask

摘要

A method for forming a reduced size contact hole over a structure. The method comprises the steps of: forming a dielectric layer on said structure; forming a polysilicon layer on said dielectric layer; forming a silicon nitride layer on said polysilicon layer; forming a photoresist block on said silicon nitride layer to cover a portion of said silicon nitride layer defining a contact hole region; removing portions of said silicon nitride layer left uncovered by said photoresist block; removing said photoresist block; forming field oxide isolation regions using said silicon nitride layer as a mask, said field oxide isolation regions having bird's beaks penetrating under said silicon nitride layer; removing said silicon nitride layer, thereby exposing a portion of said polysilicon layer left exposed by said field oxide isolation regions; etching said polysilicon layer using said field oxide isolation regions as a first mask; and etching said dielectric layer using said polysilicon layer as a second etching mask.