Method of forming a trench capacitor with a sacrificial silicon nitrate

Abstract

The present invention provides a method of forming trench capacitor with a sacrificial silicon nitride. A deep trench structure is formed in a substrate. A TEOS oxide layer is formed on the substrate and filled in said trench region, etched to a first level subsequently, wherein a portion of the TEOS oxide layer is remained in the trench region and a portion of the substrate exposed to form a trench sidewall. A thermally oxidation process is performed to form a collar oxide on the exposed substrate. A silicon nitride sidewall is formed on the collar oxide, then removing the residual TEOS oxide layer by wet etching. A bottom cell plate is formed in the lower trench region. The silicon nitride sidewall is removed. A dielectric film is formed along a surface of the bottom cell plate, the collar oxide, and the substrate, subsequently, a first conductive layer is formed on said dielectric film and refill in the trench region. The first conductive layer and the dielectric film are etched to the first level to expose a portion of the collar oxide, the exposed portion of the collar oxide is then etched by wet etching. A second conductive layer is formed on the first conductive layer and etched back to form a buried strap in the trench region.