Two-Dimensional Simulation of Single Event Indujced Bipolar Current in CMOS Structures

Single particle effects are analyzed using an advanced two-dimensional transient numerical simulator. Layered structures representative of an n-channel MOSFET drain in a p-well are modeled. TWo major results have been obtained. First, the well structure inherently provides better charge collection at the well-substrate compared to the drain-well junction. Ihis provides single event protection for the drain node. Second, large charge density tracks generated by very high energy particles can forward bias the drain-well junction resulting in bipolar action from the inherent parasitic n-p-n transistor of the well structure. This bipolar current is opposite to the photocurrent, suggesting a different SEU protection mechanism. However, it opens the possibility of upset of the "on" n-channel and, most critically, provides a mechanism for triggering latch-up in CMOS circuits.