“Non-Hydrogen-Transport” Characteristics of Dynamic Negative-Bias Temperature Instability

It has been proposed that negative-bias temperature instability (NBTI) is driven by interface-state generation, rate limited by hydrogen
transport
. In this letter, we examine dynamic NBTI characteristics and present evidence which does not conform to a hydrogen-transport model. It is observed that the amount of recovery of the threshold voltage shift |Δ
V_t
| remains constant, independent of the number of stress/recovery (SR) cycles. This behavior is inconsistent with the hydrogen-transport model, which stipulates that the amount of |Δ
V_t
| recovery should decrease with increase in the number of SR cycles. Results show that dynamic NBTI is made up of a symmetric "switching hole-trap" mechanism superimposed on a background of relatively permanent deep-level hole trap and interface-state generation.