Impact of Crystalline Phase of Ni-FUSI Gate Electrode on BTI and TDDB Reliability of HfSiON MOSFETs

Abstract

We investigated the mechanisms of bias temperature instability (BTI) and time dependent dielectric breakdown (TDDB) of phase-controlled-Ni-FUSI/HfSiON that has an electrode of NiSi and Ni3Si. A NFET-PBTI did not degrade and the electron trap density remained low even with a higher Ni-content electrode. On the other hand, NFET-TDDB degraded with a Ni3Si electrode. The decrease was related to a degradation in insulator quality near the gate dielectrics/Si interface that was enhanced by a compressive mechanical strain due to the gate electrode. NBTI of PFET did not degrade with a Ni 3Si electrode, but the main NBTI component changed from interface trap generation to hole trapping of the gate dielectrics. PFET-TDDB was improved by using NiSi and Ni3Si instead of p+ poly-Si. We attribute this improvement to a reduction in electron energy at the anode. Thus, the NFET: NiSi and PFET: Ni3Si is judged to be a superior combination for both of reliability and initial characteristics