Impact of Nitrogen Incorporation in SiOx/HfSiO Gate Stacks on Negative Bias Temperature Instabilities

The impact of nitridation anneal of Hf-silicates based metal-gated pMOSFETs on negative bias temperature instability (NBTI) is investigated. Non-nitrided stacks annealed in N₂ or O₂ and nitrided stacks either annealed in NH₃ or exposed to decoupled plasma nitridation (DPN) are measured. For non-nitrided stacks, NBT degradation is mainly due to fast-states generation. A much enhanced NBT degradation is observed, in nitrided stacks due to the additional generation of slow states. 10 years lifetime are not reached in the nitrided stacks. A physical model, based on the field enhanced hole trapping in the dielectric during NBTI stress, is proposed to simulate slow-states generation