The impact of la-doping on the reliability of low Vth high-k/metal gate nMOSFETs under various gate stress conditions

La-doped HfSiO samples show lower threshold voltage (V
_th
) and gate current (I
_gate
), which is attributed to dipole formation at the high-k/SiO
₂
interface. At low and intermediate field stress, La-doped devices exhibit better immunity to positive bias temperature instability (PBTI) due to their lower charge trapping efficiency than the control HfSiO, which mainly results from a dipole-induced greater barrier offset. However, the primary cause for defect generation at high field stress is attributed to the La atoms in the interfacial SiO
₂
layer. By optimizing the technique to incorporate nitrogen into the bottom interface, this high field reliability issue can be minimized while maintaining good device characteristics.