Pulse waveform dependence on AC bias temperature instability in pMOSFETs

In this letter, the waveform effects on the degradation enhancement of pMOSFETs under high-frequency (≥10⁴ Hz) bipolar-pulsed bias-temperature (BT) stresses were systematically studied. The enhancement was found to be mainly governed by the fall time (t_F) of the pulse waveform, namely, the transition time of the silicon surface potential from strong accumulation to strong inversion, rather than the pulse rise time (t_R) and the pulse duty factor (D). The enhancement decreases significantly with t_F increasing, and is almost eliminated when t_F is larger than ∼60 ns. This new finding is consistent with our newly proposed assumption that the recombination of free holes and trapped electrons at the SiO₂/Si interface and/or near-interface states can enhance the interface trap generation.