Technology Dependence of Stuck Bits and Single-Event Upsets in 110-, 72-, and 63-nm SDRAMs

Three synchronous dynamic random access memories (SDRAMs) from the same manufacturer with technology node sizes 110, 72, and 63 nm, were investigated under proton irradiation and using scanning electron microscope (SEM). The radiation-induced faults were characterized and compared between the different part types. The devices under test (DUTs) were irradiated with protons and experienced single-event effects (SEEs) in the form of stuck bits and single-bit upsets (SBUs). Analysis of the data retention times of bits which had SBU and were stuck during irradiation showed similar patterns of retention-time degradation, suggesting that the SBUs and stuck bits in all the three part types could be induced by the same mechanism. Detailed data retention-time analyses were also performed before and after irradiation to investigate the evolution of data retention times after irradiation and after periods of annealing. The largest radiation-induced retention-time losses were found to anneal, but the bits least affected directly after irradiation experienced decreasing data retention time as a function of annealing time. SEM imaging showed differences in the memory cell structure between the tested part types. The largest node size device was the most sensitive to radiation, both for SEE and cumulative radiation effects.