Long term charge retention dynamics of SONOS cells

We present a model for charge retention dynamics in SONOS non volatile memory cells which accounts for the space and energy distributions of the trapped charge in the silicon nitride, self consistently with the potential. Long term retention measurements (beyond 106106 s) versus temperature allowed us to decouple two charge loss mechanisms, to calibrate the model parameters and then to reproduce a large set of measurements on devices featuring different gate stacks, initial threshold voltages (including negative ones) and operation temperatures. A detailed analysis has been also carried out to compare the retention dynamics of cells featuring thin or thick tunnel oxide barriers.