Isolation formation process with active area protection

摘要

An isolation formation process that minimizes bird's beak encroachment and preserves gate oxide integrity in the active region. Future active areas are protected by a structure having a central protective material layer, such as a thermal oxide, surrounded by a ring of thermal nitride. The thermal nitride and central protective material are coated by active region protection masking covers. In one embodiment, the masking covers include sidewalls over the thermal nitride ring. In another embodiment, the central protective material layer is overetched beneath an undercut covering layer to provide an undercut filled by the sidewall. All of these features contribute to bird's beak encroachment prevention which may be narrowed to as little as 0.07 microns per side.