PBTI for N-type tunnel FinFETs

This paper reports the positive bias temperature instability (PBTI) characteristics for n-type fin-channel tunnel field-effect transistors (TFETs) with high-k gate stacks. The subthreshold slope (SS) is not degraded at all while the threshold voltage (V_th) shifts in the positive direction by the PBTI stress. The activation energy of ΔV_th for TFETs is almost the same as FinFETs, indicating that the PBTI mechanism for TFETs is almost the same as FinFETs. It was found that by applying a positive bias to the n⁺-drain, the PBTI lifetime is dramatically improved as compared with that in the conventional stress test. This is because carrier injection from the n⁺-drain is the main cause of the PBTI, especially for n-type TFETs. Thus, to accurately predict the PBTI lifetime of n-type TFETs, it is necessary to apply a drain bias for the reliability test.