Patent ID: 6271079
Filing Date: 2001-08-07
Classification: H01L

Abstract:
A method of forming a trench capacitor with a sacrificial silicon nitride sidewall, said method comprising the steps of:providing a silicon substrate;patterning said silicon substrate to form a trench region in said substrate;forming a silicon oxide layer on said silicon substrate and in said trench region;etching said silicon oxide layer to a first level, wherein a portion of said silicon oxide layer is remaining in said trench region, thereby a portion of a trench sidewall of said trench region is exposed;forming a collar oxide on said portion of said trench sidewall;forming a silicon nitride sidewall on said collar oxide;removing said portion of said silicon oxide layer in said trench region to expose a bottom portion of said trench region;etching said bottom portion of said trench region to form a fresh trench region, wherein said process is done by using said silicon nitride sidewall as a barrier;doping ions over said fresh trench region to form a bottom cell plate;removing said silicon nitride sidewall;forming a dielectric film along a surface of said bottom cell plate, said collar oxide, and said silicon substrate;forming a first conductive layer on said dielectric film and refilling in said trench region;etching said first conductive layer to a second level to form a storage node of said trench capacitor and exposing a portion of said collar oxide;etching said exposed dielectric film and portion of said collar oxide;forming a second conductive layer on said first conductive layer; andetching back said second conductive layer to a third level to form a buried strap in said trench region.