Impact of Back-Gate Bias and Device Geometry on the Total Ionizing Dose Response of 1-Transistor Floating Body RAMs

In this paper we investigate how geometry impacts the memory characteristics of 1-transistor dynamic floating body RAMs (FBRAMs) under total ionizing dose exposure. FBRAMs are implemented using fully depleted silicon-on-insulator devices with ultrathin buried oxide and body. Analytical models and experimental data are used to quantify the effects of charge trapping in the oxides and spacers on the memory read window shifts. The effects of increased radiation-induced leakage and interface trapping on the retention time are also discussed. Small geometry devices show reduced memory window shifts compared to large devices, but the retention time degradation is higher. The effects of coupling between interfaces and back-gate bias are also discussed in the context of memory characteristics.