THE EFFECTS OF X-RAY IRRADIATION-INDUCED DAMAGE ON RELIABILITY IN MOS STRUCTURES

Abstract

The effects of X-ray irradiation induced damage on long-term reliability of MOS structures have been investigated. The gate leakage currents at low electric field during a measurement of Fowler-Nordheim tunneling were increased after X-ray exposure, it was explained by the interface trap-assisted tunneling mechanism. This leakage component was completely eliminated by forming gas annealing at 450 degrees C. The long-term reliability of MOS gate oxide is significantly affected by the residual damages in the oxide even after forming gas annealing. In X-ray damaged MOS structures, the average values of cumulative charge-to-breakdown (Q(bd)) were reduced about 15% as compared with the unexposed devices. The major mechanism responsible for reduction of Q(bd) in irradiated devices is enhanced electron trapping into the neutral traps.