Robust shallow trench isolation technique used for 75nm nor flash memory

We have developed a new Self-aligned poly (SAP) process to improve the tunnel oxide integrity by optimizing the shallow trench isolation (STI) corner rounding profile and reducing the local oxide thinning effect. It is found that double in-situ steam generation (ISSG) liner oxides can effectively improve the STI corner rounding. As for the local oxide thinning effect, the composite pad dielectrics (C-Pad) composed of SiO₂/poly-Si are good to prevent local thinning of tunnel oxide at STI corner. Moreover, using ISSG tunnel oxide can further reduce the local oxide thinning effect. Excellent breakdown characteristics of tunnel oxide by optimizing the key technologies have been verified in this work.