Radiation effects in nitride read-only memories

We report on the influence of different types of radiation on the nitride read-only memories (NROM ). The memory cells were irradiated by light ions (Boron), X-rays and c-rays. Memory transistor parameters, such as threshold voltage and subthreshold drain leakage were studied as a function of the accumulated radiation dose and compared to the as-programmed (-erased) devices parameters. Their time evolution was registered in the range from few hours up to 5 months after the irradiation. The NROM cells showed good radiation robustness up to high accumulated doses. Sufficient program margin (difference of threshold voltage in the programmed state and the read-out voltage level) remained after c or X irradiation for absorbed doses exceeding 50 krad(Si) and 100 krad(Si), respectively. For Boron irradiation, the programmed devices remained stable up to the fluence of 1011 ions/cm2 (equivalent to 1 Mrad(Si) of TID tolerance