Method of forming a trench isolation structure resistant to hot phosphoric acid by extending trench liner to shoulder portions

摘要

A trench isolation structure is fabricated on a silicon substrate by initially depositing a masking layer of nitride having an aperture. A spacer of oxide is then formed on the inner sidewall of the aperture to define a mask window. A trench is formed in the substrate by etching it through the mask window. The spacer is removed to form stepped shoulder portions on upper edges of the trench. A liner of thermal oxide is provided in the trench, followed by deposition of a liner of nitride on an area including the trench and the stepped shoulder portions. The trench is filled with silicon oxide, and the layer of nitride is etched away with hot phosphoric acid.