Thermal Neutron-Induced Single-Event Upsets in Microcontrollers Containing Boron-10

Single-event upsets (SEUs) were measured in thermal neutron-irradiated microcontrollers with 65- and 130-nm-node static random-access memories (SRAMs). The suspected upset mechanism is charge deposition from the energetic byproducts of10B thermal neutron capture. Although elemental analysis confirmed that both microcontrollers contain10B, only the 65-nm node microcontroller exhibited a strong response to thermal neutrons. Monte Carlo simulations were performed to investigate the effects of11B enrichment on thermal neutroninduced SEUs in a 65-nm SRAM node when boron is present in the p-type well, p-type source and drain, or tungsten plug. Simulations indicate that the byproducts of10B(n, α)7Li reactions are capable of generating sufficient charge to upset a 65-nm SRAM. The highest amount of charge deposition from10B(n, α)7Li reaction byproducts occurs when natural boron is used to dope the p-type source and drain regions. Simulations also show that the SEU cross section is nonnegligible when11B-enriched boron is used for doping.