Impact of Crystalline Phase of Ni-FUSI Gate Electrode on Bias Temperature Instability and Gate Dielectric Breakdown of HfSiON MOSFETs

We investigated the influences of gate metals (n⁺/p⁺ poly-Si, Ni silicide (NiSi), Ni₃Si) on the time dependent dielectric breakdown (TDDB) reliability and negative/positive bias temperature instability (NBTI/PBTI) of phase-controlled Ni-full-silicide (Ni-FUSI)/HfSiON/SiO ₂ FETs. The TDDB reliability of NiSi-electrode n-FETs was comparable to that of n⁺-poly-Si-electrode n-FETs. However, further Ni enriching of the electrode to Ni₃Si degraded the reliability. A degradation of the base SiO₂ layer seems to have been responsible for this. A higher compressive strain was observed for the Ni₃Si sample, which may have caused the degradation of the bottom SiO₂. In contrast, the TDDB reliability of p-FETs improved much by using Ni₃Si. We attribute this improvement to the lower cathode energy and/or the absence of boron in the gate electrode. The PBTI of the n-FETs was negligible and was not degraded by Ni enrichment of the gate electrode and additional annealing, suggesting that HfSiON was stable against the Ni-FUSI process. The threshold voltage (V_T) shift in NBTI of p-FETs did not depend much on the gate materials. The major component of the V _T shift in NBTI, however, was changed by Ni enriching from the generation of interface traps to the trapping of holes by the HfSiON bulk