Total Ionizing Dose Effects on DRAM Data Retention Time

Dynamic random access memory (DRAM) data retention time degradation induced by radiation exposure is investigated in this paper. We present the experimental setup and the results of total ionizing dose (TID) test on a COTS SDRAM device. We observed a significant retention time reduction related to the absorbed dose and we assume radiation induced interface trap generation as the origin of the retention time reduction. By measuring individual cells retention time before and after radiation exposures, we found out that the reduction is not homogeneous among cells: the amount of leakage current increase depends on the position and the energy level of the generated trap, leading to a wide distribution of retention time reduction. Of particular interest is the fact that device was unbiased during irradiation and that no post-irradiation recovery was observed.