Investigation of Proton and X-Ray Irradiation Effects on Nanocrystal and Floating Gate Memory Cell Arrays

We compared the radiation tolerance of nanocrystal and floating gate memories, fabricated with the same technology. We investigated the effects of 5-MeV proton and 10-keV X-ray irradiations, focusing on the charge loss, the permanent degradation of the electrical characteristics, and the data retention. We also presented a first order model of the charge loss and the permanent threshold voltage shift. The model and the experimental results show that nanocrystal memories feature improved radiation robustness against total ionizing dose. Nanocrystal memories can withstand a radiation dose 3 and 10 times larger than floating gate memories, in terms of charge loss and data retention, respectively.