THE DETERMINATION OF SI-SIO2 INTERFACE-TRAP DENSITY IN IRRADIATED 4-TERMINAL VDMOSFETS USING CHARGE-PUMPING

The utility of charge pumping to measure Si-SiO2 interface trap densit y in irradiated four-terminal VDMOSFETs is demonstrated. A modificatio n of the conventional charge pumping approach is employed, where recom bination of charge through interface traps in the neck region is measu red in the drain. Three components of drain current resulting from the charge pumping measurement are identified. When the device is properl y biased, charge pumping current can be separated from the other compo nents of drain current and modeled over a wide range of interface trap densities using standard charge pumping theory. When sources of error are accounted for, radiation-induced interface trap densities measure d with charge pumping are in good quantitative agreement with those es timated with the midgap charge separation and subthreshold hump techni ques.