Impact of neutron flux on soft errors in MOS memories

Investigation of the effect of neutrons on MOS memory devices showed that such devices are sensitive to neutrons. Neutron irradiation of DRAMs and SRAMs caused bit errors due to soft errors; however, no errors occurred in FRAMs and flash memories. The irradiation of alpha-rays caused only single-bit-errors, but when neutrons were irradiated, both single-bit-errors and adjacent multi-bit-errors (about 5% of the total) occurred on our results. Soft errors in RAM were estimated not to occur when the energy of the neutron particles is about 5 MeV or less. Two tendencies were identified between the error rate and the collected charge, depending on the device structures. In particular, presence of a triple-well played a significant role for lowering the error rate. Simulation using a simplified two-dimensional model produced results close to the experiment results, in terms of error mode and device configurations.