Analysis Of Sram Neutron-Induced Errors Based On The Consideration Of Both Charge-Collection And Parasitic-Bipolar Failure Modes

This paper describes an investigation of the upsetting of values in cells hit by alpha particles or neutrons, in which the feedback operation of the cross-coupled inverter in SRAM is accurately modeled through simultaneous device and circuit simulation. We demonstrate, for the first time, the existence and mechanism of a new parasitic-bipolar-failure (PBF) mode. Accurate values of critical charge (Q(cg)) for failure are calculated for both this mode and the conventional charge-collection-failure (CCF) mode. We identify opposite behaviors of Q(cg) for the CCF and PBF modes with respect to the amount of charge at the storage node (Q(node)). The results on critical charge are also used to predict the soft-error rate and the prediction agrees with the results of measurement to within 30%. Based on the results, we propose design techniques for reduced SER.