Method of fabricating a shallow trench isolation by using oxide/oxynitride layers

摘要

A stacked layer including a first oxide, a nitride layer, a second oxide layer and an oxynitride layer is formed on the top of the first oxide layer. An etching is performed through a photoresist to etch the oxynitride, the second oxide and nitride. Oxide spacers are formed on the side walls of the pattern structure, the oxynitride layer is also removed during the formation of the oxide spacers. Trenches are generated by a dry etching technique. The second oxide and the oxide spacers are removed. Next, a thermal oxidation is performed to rounding the corners of the trench openings. A gap filling material is refilled into the trenches and formed on the nitride. Next, a chemical mechanical polishing (CMP) is used to remove the top of the CVD-oxide and the nitride layer. The residual nitride layer, the CVD-oxide and pad oxide are removed to create trench isolation structures with rounding corners.