Impact of TiN Metal gate on NBTI assessed by interface states and fast transient effect characterization

With the decrease of the high-k layer thickness, NBTI becomes more critical than PBTI. The relative contribution of interface states and trapping on NBTI is analysed in Hf-based stacks. Dit density and generation kinetics were found to be similar to that in SiO₂, whereas a very large fast trapping component was evidenced. The pre-existing traps responsible for this fast trapping effect were related to N incorporation in the interfacial layer after TiN PVD deposition. Finally, a significant lifetime improvement is achieved using TaC as gate material.