Mechanism of AC-stress-induced leakage current in EEPROM tunnel oxides

A new model is proposed for the AC-stress-induced leakage current in flash EEPROM tunnel oxides. This model is based on tunneling trap sites generated (increased leakage) during the on-time of a stress pulse and deactivated (decreased leakage) during the off-time. We have characterized this neutralization effect and its role in the reduction of the AC-stress-induced leakage current. Using the model developed in this work, the optimum programming waveform to minimize leakage current is a long single pulse with the reverse polarity bias during the long off time in the case that the total on and off time is constant. This reduction in stress-induced leakage current is critical to minimizing read disturb errors in flash EEPROMs.