Preventing gate oxice thinning effect in a recess LOCOS process

摘要

Embodiments of the present invention relate to a method for preventing gate oxide thinning in a recess LOCOS process. A method of forming a gate oxide on a substrate comprises providing a substrate having thereon a plurality of trenches having gate oxides formed therein, wherein the plurality of trenches are separated by a patterned pad oxide and a patterned silicon nitride layer disposed thereon and used to form the plurality of trenches. The patterned silicon nitride layer and the patterned pad oxide layer are removed to expose a surface of the substrate as an active area of the semiconductor device. An ion drive-in to the active area on the substrate is performed by directing a flow of oxygen and nitrogen toward the substrate at a predetermined temperature and with a sufficient amount of oxygen to at least substantially prevent silicon nitride from forming on the field oxide regions. The method further comprises forming a sacrificial oxide layer on the active area, removing the sacrificial oxide layer to expose the active area, and forming a gate oxide layer on the active area. The affinity for oxygen with silicon is higher than that for nitrogen with silicon. As a result, oxygen can be used to prevent or reduce silicon nitride formation on the field oxide regions.