Modeling of Heavy Ion Induced Charge Loss Mechanisms in Nanocrystal Memory Cells

We present the first charge loss model of heavy ion induced radiation damage on nanocrystal memory cells. The model takes into account the nanocrystal distribution non uniformity and the effect of different programming techniques, which may produce non uniform charging of the nanocrystals. The model has been validated with a focused microbeam test. It provides an estimation of both the ion track size and the average number of ion hits required for achieving a given charge loss. In our irradiation experiments we estimated an ion track size (diameter) of 85 nm for 50-MeV Cu ions. This model confirms also the good robustness of nanocrystal memories against heavy ion irradiation and their much stronger tolerance than the conventional floating gate based memories.