Effect of Nitridation of Hafnium Silicate Gate Dielectric on Positive Bias Temperature Instability in pMOS Devices

A detailed investigation of the effect of nitridation of hafnium silicate on positive bias temperature instability (PBTI) in n(+)-polySi gate pMOS capacitor structures has been presented. Our analysis shows that nitridation improves the intrinsic oxide breakdown field, reduces the equivalent oxide thickness (EOT) and as-grown surface state density D-it by an order of magnitude. On the other hand, like NBTI degradation, nitridation significantly enhances PBTI degradation in pMOS devices causing reduction in PBTI lifetime at a given applied voltage V-G. However, both nitrided and non-nitrided gate stacks reaches 10 year lifetime at an applied gate bias of 1.2 V.