New corner rounding process for sub-0.15 μm shallow trench isolation

To obtain a top corner rounding in the Shallow Trench Isolation (STI) process with a hard mask, a new etching spacer and Si soft etching for an useful top corner process is evaluated. This technique utilizes the oxide rounding and, thus, effectively suppresses the inverse narrow width effect due to the stress reduction at the top corner and the less interface influence between active and field oxide. Also this technique showed no degradation of junction leakage current and less profile micro-loading effect compared with the conventional resist mask process. As a result, it has been found that this technique is very effective for sub-0.15 μm STI formation