Bias Temperature Instability in MOSFETs with Atomic-Layer-Deposited Si-Nitride/SiO2 Stack Gate Dielectrics

Compared with conventional SiON MOSFETs, p⁺-poly-Si gated MOSFETs with atomic-layer-deposited Si-nitride/SiO₂ stack gate dielectrics exhibit quite different bias temperature instability (BTI) behaviors: NMOS under positive BT stress degrades significantly with the stress voltage increasing; PMOS under negative BT stress exhibits a turnaround threshold voltage shift; etc. The abnormal BTI behaviors indicate the existence of preexisting traps in the stack film, most probably at the SiN/SiO₂ interface