POSTIRRADIATION BEHAVIOR OF THE INTERFACE STATE DENSITY AND THE TRAPPED POSITIVE CHARGE

The post-irradiation behavior of the energy distribution of interface states, Dit, and of the trapped positive charge, Not, of MOS devices is studied. The shift of interface state density from the broad peak at 0.7 eV to below midgap is found to be reversible. The direction of the shift is determined by the surface potential. The post-irradiation introduction of hydrogen into the gate oxide increases the interface state density across the bandgap and decreases Not by a similar amount. Following the introduction of hydrogen, the reversibility of Not is increased by an order of magnitude. These effects show the connection between the the exprimental conditions and the type of post-irradiation behavior that is observed. This paper also discusses models for the hydrogen induced Dit buildup and for the reversibility of Dit and Not. © 1990 IEEE