On electron-trap transformation and its unexpected frequency dependence under dynamic positive-bias temperature stressing

In the course of our study on the frequency dependence of dynamic positive-bias temperature instability (PBTI) in the HfO₂/TiN gate n-MOSFET, an unexpected result was obtained. In accordance with our recent study, electron trapping is observed to gradually evolve into a more permanent form, suggesting that some shallow electron traps are converted into deeper ones as the PBTI stress progresses. Interestingly, however, this evolution is found to exhibit a positive dependence on the gate frequency, i.e. the fraction of electron trapping that is rendered more permanent is increased with the gate frequency over the range of frequency studied (1 mHz - 1 MHz).