We present excellent performance and reliability characteristics of a Silicon nanocrystal (Si-nc) 4 Mb NOR Flash array (90nm technology node). Main original technological improvements are a cylindrical symmetry of the 1-Transistor bitcell, which significantly increases the coupling ratio (particularly critical in Si-nc memories), and the use of an optimized ONO control dielectric, which prevents from parasitic charge trapping during cycling. Results shown here in terms of memory performance, high temperature reliability, endurance and disturbs are, at our knowledge, outstanding compared to literature state-of-theart and demonstrate the high potential of this technology for embedded memory applications.
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, respectivel
We present new results on heavy-ion irradiation of nanocrystal non-volatile addressable memory arrays. We show that the effects of a single ion hit are negligible on these devices due to the discrete nature of the storage sites. We estimate that, in order to observe an appreciable threshold voltage shift, at least three-four ion hit are needed. Despite several cells experienced multiple hits they are still functional after the irradiation, showing no changes on the retention characteristics. These results highlights an outstanding improvement of the nanocrystal technology over the conventional floating gate memories in terms of radiation tolerance, which are encouraging for a potential application in radiation-harsh environments
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