GATE SIZE DEPENDENCE OF THE RADIATION-PRODUCED CHANGES IN THRESHOLD VOLTAGE, MOBILITY, AND INTERFACE STATE DENSITY IN BULK CMOS

We have observed that radiation-induced threshold voltage shifts, interface trap densities, and channel mobility reductions are dependent on the drawn or coded geometrical sizes of transistors in one radiation-hardened VLSI CMOS technology. In another technology, no such dependencies were found. The purpose of this paper is to report our data, to suggest physical mechanisms responsible for the observed size dependencies, and to warn that large-area transistors and capacitors for total dose evaluations may not always be suitable. Stress measurements indicate that the radiation-induced changes are correlated with higher tensile stress levels.