Deep trench isolation region with reduced-size cavities in overlying field oxide

摘要

According to an exemplary method for removing a hard mask in a deep trench isolation process, a hard mask is formed over the substrate, where the substrate includes at least one field oxide region. Thereafter, a trench is formed in the substrate, where the trench has a first sidewall and a second sidewall. According to this exemplary embodiment, the hard mask is removed after forming the trench. The hard mask may be removed by, for example, etching the hard mask in an anisotropic dry etch process, where the anisotropic dry etch process is selective to nitride and silicon. Next, an oxide liner is deposited by a CVD process on the first and second sidewalls of the trench and over the substrate after the hard mask has been removed.