Method for a consistent shallow trench etch profile

摘要

For use with a sub-micron semiconductor process, a trench isolation process improves the etch profile of trenches among dense and isolated lines. In an example embodiment, a process forms a dielectric stack of silicon dioxide, silicon nitride and silicon oxynitride on a silicon substrate. Photolithography and etch define trench regions in the silicon substrate through the dielectric stack. Silicon oxynitride acts as a hard mask reducing differences in the sidewall slope among dense areas of the semiconductor device and the sparse areas of the semiconductor device.