Radiation effects on gate induced drain leakage current in metal oxide semiconductor transistors

The gate induced drain leakage current (Idl) of metal oxide semiconductor (MOS) transistors changes significantly when the devices are exposed to ionizing radiation. For n-channel MOS transistors, Idl decreases, whereas for p-channel devices, it increases. The change of leakage current at higher tunneling fields is proportional to the increase of hole trap density in the gate oxide region. The leakage current measurement technique is a useful tool for characterizing radiation effects in MOS transistors because at higher bias it is dependent on increase of oxide charge while independent of interface states. The annealing of trapped charges at the tunnel junction is faster than in the channel region as determined from subthreshold characteristics. The results of the thermal annealing experiment reveal that the drain current in the control region is attributed to interface state assisted tunneling.