A new wafer level reliability method for evaluation of ionic induced pmosfet drift effects

An ionic induced pMOSFET drift effect was investigated by deliberately enhancing the sodium concentration in interlevel dielectric layers. High frequency capacitance voltage and triangular voltage sweep (TVS) measurements as well as different bias temperature stress sequences were employed to show that the degradation is a two step process: sodium drift into active areas and charging of traps which were generated by sodium interactions with the semiconductor oxide interface. A special wafer level reliability method was developed which takes into consideration the two phase nature of the failure mechanism.