THE SIMULATION OF PULSED-IONIZING - RADIATION-INDUCED ERRORS IN CMOS MEMORY CIRCUITS

The effects of transient ionizing radiation on complementary metal-oxide-semiconductor (CMOS) memory circuits has been studied by computer simulation. Simulation results have uncovered the dominant mechanism leading to information loss (upset) in dense (CMOS) circuits: 'rail span collapse.' This effect is the catastrophic reduction in the local power supply at a RAM cell location due to the conglomerate radiation-induced photocurrents from all other RAM cells flowing through the power supply interconnect distribution. Rail span collapse leads to reduced RAM cell noise margins and can predicate upset. The results of this work show that rail span collapse is the dominant pulsed radiation effect in many memory circuits, preempting local circuit responses to the radiation.; Several techniques to model power supply noise, such as that arising from rail span collapse, are presented in this work. These include an analytical model for design optimization against these effects, a hierarchical computer analysis technique for efficient power bus noise simulation in arrayed circuits, such as memories, and a complete circuit simulation tool for noise margin analysis of circuits with arbitrary topologies.