Impact of Crystalline Phase of Ni-Full-Silicide Gate Electrode on TDDB Reliability of HfSiON Gate Stacks

We investigated the influences of gate metals (poly-Si, NiSi, Ni
₃
Si) on the time dependent dielectric breakdown (TDDB) reliability of phase-controlled Ni-full-silicide/HfSiON n-FETs. The TDDB reliability of the NiSi-electrode FETs was comparable to that of poly-Si-electrode FETs. However, the reliability was degraded by further Ni-enriching to Ni
₃
Si. We presume that the degradation of the base SiO
₂
layer is responsible for this. We do not relate the TDDB degradation to Ni diffusion into the insulator, but rather to the strain that is higher in Ni
₃
Si samples