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MOS capacitors with a 4.4 nm thick gate oxide have been exposed to gamma radiation from a Co-60 source. As a result, we have measured a stable leakage current at fields lower than those required for Fowler-Nordheim tunneling. This Radiation Induced Leakage Current (RILC) is similar to the usual Stress Induced Leakage Currents (SILC) observed after electrical stresses of MOS devices. We have verified that these two currents share the same dependence on the oxide field, and the RILC contribution can be normalized to an equivalent injected charge for Constant Current Stresses. We have also considered the dependence of the RILC from the cumulative radiation dose, and from the applied bias during irradiation, suggesting a correlation between RILC and the distribution of trapped holes and neutral levels in the oxide layer

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Flash memories are the most important among modern nonvolatile memory technologies. We are showing new results on the threshold voltage shifts in Flash memory arrays after 60 Co irradiation. A (relatively) high total dose, exceeding 100 krad (SiO 2 ), is needed to induce errors in the array, but threshold voltage shifts are all but negligible even at lower doses. These shifts can be accurately described by using a model which considers the charges generated by irradiation in all the oxides surrounding the floating gate. We are also showing that cycling (endurance) and total ionizing dose effects mutually add.