Highly-scaled SRAM immunity to MNU based on analysis of an induced parasitic bipolar effect

Three-dimensional TCAD simulation is used to explore a new charge-collection mechanism in highly-scaled MOSEFT. The results show the charge collection with the parasitic bipolar conduction can cause an increased SEU sensitivity. Then the problem of multiple-node upset in a 0.18μm 12-T SEU hardened SRAM cell is also studied. Unlike traditional multiple node charge collection in which diffusions near a single event strike collect the deposited carriers, a novel mechanism involves direct drift-diffusion collection at a NFET transistor in conjunction with parasitic bipolar conduction in nearby PFET transistor. The charge collection with the parasitic bipolar conduction compromise the SEU hardened design, thus causing upsets.