STI Gap-Filling Performance Improvement by the Process Integration Optimization in the 4XNM ETOX NOR Flash

The gap-fill performance of shallow trench isolation (STI) plays an important role in the cell size shrink of ETOX Nor flash. In this work, we optimize the SIN pullback and high-density plasma (HDP) process to improve STI gap-fill, and the gap-fill performances are investigated by the wafer accept test (WAT) and chip probe (CP). And the void-free gap-fill and the comparable WAT/CP performance are achieved by the process integration of SIN pullback with suitable HPO dosage and the optimized Dep-Etch-Dep cycle of HDP.