Modeling of ionizing radiation effects in short-channel MOSFETs

A charge-sheet approach is employed to model the effects of ionizing radiation on short channel MOSFETS, where the primary effect is the introduction of oxide-trapped charges (OTC) and interface-trapped charges (ITC). The two-dimensional charged sheet model is used to study transistors with channel lengths of 0.27-4.65 microns. ITC and OTC are found to cause significant effects in each region of operation, with an exponential sensitivity of drain current to these changes in the subthreshold region, while the effects of both ITC and OTC in the triode region are indistinguishable from two-dimensional charge sharing effects. This implies that a simple threshold voltage offsets analysis in short channel MOSFETS cannot provide a physical separation of two-dimensional effects from radiogenic effects. The fixed charge component contributed by ITC and OTC to the channel charge in the saturation region can shift the critical field point at the edge of the channel pinch-off region, altering the formation of a 'knee' region of the output characteristic.