Plasma-process-induced damage in sputtered TiN metal-gate capacitors with ultrathin nitrided oxides

A comprehensive study on plasma-process-induced damage (P2ID) in sputtered TiN metal-gated devices with 4 nm N₂O-nitrided oxide was performed. We found that the TiN metal-gated devices exhibit a significant 8 angstroms reduction in the effective oxide thickness, due to physical damage caused by sputtering and/or oxide consumption during the postannealing step. We also found that the postdeposition rapid thermal annealing (RTA) temperature affects both the flat-band voltage (V_fb) and the interface state density (D_it). Furthermore, degradation in the gate-oxide integrity caused by severe charging damage by the additional plasma processes in the TiN metal gate process flow was also observed. The P2ID leads to significant degradation in the charge-to-breakdown and a gate leakage current increase, even for the genuinely robust nitrided oxide used in this study. Finally, N₂ plasma posttreatment was proposed as an effective method for suppressing the gate leakage current.