Polysilicon coated swami (sidewall masked isolation)

摘要

A side wall masked isolation (SWAMI) technique for isolating active regions on an integrated circuit involves reducing the "bird's beak" structure. The technique involves forming an isolation recess in the substrate, and then lining the recess with a layer of silicon dioxide, and then a layer of silicon nitride. Then, oxide spacers are formed on each of the sidewalls of the recess. The recess is then anisotropically etched until the substrate at the bottom of the recess is exposed. This etch process involves removing portion of both the silicon dioxide and the silicon nitride layers formed at the bottom of the recess. Subsequently, a layer of polycrystalline silicon material is deposited in the recess and is then etched back and oxidized to form a field oxide. Since the polycrystalline silicon is oxidized, the result is negligible oxide encroachment resulting in a reduction in the "bird's beak" structure.