Improved immunity to plasma damage in ultrathin nitrided oxides

Plasma-induced damage in various 3-nm thick gate oxides (i.e., pure O₂ 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 the wafer center as well as at 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 ultrathin oxides in charge-to-breakdown measurements. Additionally, ultrathin N₂O-nitrided oxides show superior immunity to charging damage, especially for pMOS devices.