EFFECT OF TUNNELING ELECTRONS IN FOWLER-NORDHEIM REGIME ON THE CURRENT-VOLTAGE CHARACTERISTICS AND MODEL OF DEGRADATION OF METAL-OXIDE-SEMICONDUCTOR CAPACITORS

The evolution of the shift of current-voltage characteristics after Fo wler-Nordheim stress has been investigated. In some cases, a diminutio n of the slope of current-voltage characteristics was observed. It has been studied and discussed with respect to the mode of the injection of carriers in the oxide, the type of carrier trapping, and the genera tion of defects. The variation of the slopes of current-voltage charac teristics after high-electric-field stress is due to a nonuniformity o f the field in the oxide and mainly depends on the cathode field. The variation of the cathode field is basically related to the location of the oxide charge (positive or negative) near the substrate-Si/SiO2 an d gate/SiO2 interfaces which modify the shape of the tunneling barrier . A model of degradation of the metal-oxide-semiconductor structures h as been deduced from a qualitative analysis of voltage shifts of curre nt-voltage characteristics depending on the magnitude of electric fiel d stress, on the stress mode with a positively or negatively biased ga te, and on the injected charge density. The degradation of the oxide i s consistent with both mechanisms of trap creation and/or impact ioniz ation.