Effects of total ionizing dose on transient ionizing radiation upset sensitivity of 40–180 nm SRAMs

Effects of total ionizing dose (TID) on the transient radiation upset sensitivity of commercial static random access memories (SRAMs) were investigated. Commercial SRAMs of three technology nodes were irradiated with Co-60 gamma rays for total dose effects and with pulsed x rays generated using a “Chen-Guang” accelerator for doserate effects. It is shown that TID irradiation and the memory pattern written to the memory array during TID irradiation can substantially affect the transient radiation upset sensitivity of all the SRAMs. First, the memory pattern written to the memory array during TID irradiation is more sensitive to pulsed x rays for all SRAMs. Second, the variation in transient radiation upset sensitivity with total dose has different tendencies for different SRAMs, but the static power current increased with the increase in total dose for all SRAMs. The increase in static power current with total dose and the increasing sensitivity of the memory pattern during TID irradiation are caused by the increasing TID induced leakage current, which results in an asymmetric noise margin of individual memory cells.