A model for TID effects on floating gate memory cells

Four different technologies of floating gate (FG) memory arrays were subjected to Co-60 gamma-rays and 10 keV X-rays irradiation to evaluate their response to the total ionizing dose. The effect of irradiation was a uniform charge loss across the whole array. Irradiation effects can be modeled as the result of two phenomena, namely, the generation of charge in the dielectric layers surrounding the floating gate and its subsequent recombination and drift, and the photoemission of carriers from the charged FG. The second phenomenon is effective at high doses. As a consequence of these, two phenomena, devices featuring a smaller FG are less prone to total ionizing dose effects than devices featuring a larger FG, proper of older technological generations. We propose a model that accurately fits experimental data over a broad series of experimental conditions.