Plasma-induced charging damage in ultrathin (3 nm) nitrided oxides

Plasma-induced charging damage in various 3 nm-thick gate oxides (i.e., pure oxides and N₂O-nitrided oxides) was investigated by subjecting both nMOS and pMOS antenna devices to a photoresist ashing step after metal pad definition. Gate leakage current measurements indicated that large leakage current occurs at both the wafer center and the wafer edge for pMOS devices, while it occurs only at the wafer center for nMOS devices. These interesting observations could be explained by the polarity dependence of ultra-thin oxides in charge-to-breakdown characteristics. More importantly, our experimental results demonstrated that stress-induced leakage current (SILC) caused by plasma damage is significantly suppressed in N₂O-nitrided oxides, compared to pure oxides, especially for pMOS devices. Finally, nitrided-oxide is also found to be more robust when subjected to high temperature stressing.