Dielectric reliability studies of metal insulator metal capacitors (MIMCAP) with SiN dielectric under unipolar to bipolar AC-stress

We present AC stress and TDDB results on silicon nitride MIMCAPSs with unipolar and bipolar stress amplitudes. Two different nitride types are investigated in the frequency range of 0.1 Hz to 100 kHz. For pure bipolar stress amplitudes we find an enormous enhancement of the time to breakdown compared to the DC-reference. This enhancement is dependent on the nitride type. We propose that the strong lifetime enhancement is related to an increased trapping and an enhancement is related to an increased trapping and an enhance charge to breakdown at bipolar stress. For the non-bipolar stress case, i.e. biased AC stress, the lifetime enhancement can be estimated by a duty cycle approach which considers the effective duration of stress when fields varying over time are involved. The results confirm that a DC reliability assessment of nitride MIMCAP is worst case.