Negative bias temperature instability of p-channel metal oxide semiconductor field effect transistor with novel Hf_xMo _yN_z metal gate electrodes

The negative bias temperature instability (NBTI) characteristics of p-channel metal oxide semiconductor field effect transistor (pMOSFET) devices with novel Hf_xMo_yN_z metal gates have been investigated for the first time. The threshold voltage (V_th) shift, subthreshold swing (SS), off-leakage current, and field effect mobility (μFE) were found to be degraded after NBTI stress. The possibility of nitrogen diffusing to the oxide is increased by employing a higher N₂ ratio during Hf_xMo_yN_z deposition. The higher nitrogen content in Hf_xMo_yN_z metal gates shows threshold voltage (V_th) shift, subthreshold swing (SS), off-leakage current, and field effect mobility (μFE) degradation. The degradation of threshold voltage (V_th), subthreshold swing (SS), off-leakage current, and field effect mobility (μFE) are believed to be due to the interface states and fixed oxide charges generation from the broken Si-H bonds at the SiO₂/Si interface. Furthermore, the mechanism of NBTI degradation has been suggested by a physical model and an energy band diagram.