Semiconductor science and technology vol:14 issue:9 pages:741-746
The effect of x-ray-induced damage on the electrical characteristics of metal-oxide-semiconductor capacitors with ultrathin gate oxide and oxynitride layers is investigated. The tunnelling current of irradiated capacitors is observed to be enhanced in the low gate voltage range, a behaviour quite similar to the increased leakage current observed in electrically stressed devices. On the other hand, the slopes of the time-to-breakdown distributions decrease after x-ray irradiation, indicating that the critical density of traps needed to trigger breakdown in the gate oxide is lower in irradiated capacitors. in addition, the probability of observing soft breakdown of the SiO2 layer increases after the irradiation. These results suggest that the radiation-induced traps participate in the formation of the percolation path formed in the gate insulator at breakdown or soft breakdown.