An empirical model for charge leakage through oxide nitride oxide interpoly dielectric in stacked-gate flash memory devices

We have studied the reliability problems in the degradation of the data retention characteristics of the stacked-gate flash EEPROM devices with an oxide–nitride–oxide (ONO) interpoly dielectric. Threshold voltage shift measured as a function of bake time at all tested temperatures shows that there are two distinct phases which have different dependences on the bake temperature and time; the first phase shows a very fast shift rate of the threshold voltage while the second phase has a gradual shift rate. Based on the high-temperature accelerated test, an empirical model was developed for each phase, which explains the dominant mechanisms for the spontaneous charge leakage through the ONO interpoly dielectric.