Measurement and Analysis of Alpha-Particle-Induced Soft Errors and Multiple-Cell Upsets in 10T Subthreshold SRAM

This paper presents measurement results of alpha-particle-induced soft errors and multiple-cell upsets (MCUs) in 65-nm 10T SRAM with a wide range of supply voltage from 1.0 to 0.3 V. We reveal that the soft-error rate (SER) at 0.3 V is six times higher than that at 1.0 V and the MCU rate significantly increases in the subthreshold region. To investigate the reason for the MCU increase, the dependences of the MCU rate on the body-bias voltage and the distance between well ties are examined, and we conclude that the main cause of the MCU increase is not the parasitic bipolar effect but another mechanism, such as charge sharing. In addition, the dependence of the variation in the soft-error immunity of each memory cell on the supply voltage is examined, since SRAMs operating in the subthreshold region are sensitive to manufacturing variability. Measurement results indicate that the number of soft errors in each memory cell varies cell by cell, whereas the cause of the variation is explained by the spatial randomness of alpha-particle hits, and a distinct influence of manufacturing variability is not observed even in the subthreshold region.