Frequency dependence of TDDB & PBTI with OTF monitoring methodology in high-k/metal gate stacks

This paper deals with AC/DC effect on nMOS TDDB (Time Dependent Dielectric Breakdown) and PBTI (Positive Bias Temperature Instability) using suitable OTF (on the Fly) monitoring methodologies. First, an adapted unipolar AC stress without stress interruption is used to study TDDB dependences on frequency and duty cycle. For frequencies above 100Hz, Time to Breakdown is shown to depend significantly on these two parameters. On the other hand, in order to evidence a possible effect of trapping on TDDB, PBTI dependences on frequency and duty cycle are also studied using fast BTI measurement. Finally, trapping/detrapping mechanisms fail to explain TDDB observations.