Simultaneous single event charge sharing and parasitic bipolar conduction in a highly-scaled SRAM design

A novel mechanism for upset is seen in a commercially available 0.25 μm 10-T SEE hardened SRAM cell. Unlike traditional multiple node charge collection in which diffusions near a single event strike collect the deposited carriers, this new mechanism involves direct drift-diffusion collection at an NFET transistor in conjunction with parasitic bipolar conduction in nearby PFET transistors. The charge collection with the parasitic bipolar conduction compromise the SEE hardened design, thus causing upsets. The mechanism was identified using laser testing and three-dimensional TCAD simulations.