PHYSICAL BASIS FOR NONDESTRUCTIVE TESTS OF MOS RADIATION HARDNESS

We have found that the 1/f noise and channel resistance of unirradiated nMOS transistors from a single lot with various gate-oxide splits closely correlate with the oxide-trap and interface trap charge, respectively, following irradiation. The 1/f noise is explained by a trapping model, while the variations in channel resistance are explained by scattering from interface-trap precursor defects. It appears that both noise and channel mobility measurements may be useful in defining nondestructive hardness assurance test methods for devices fabricated from a single technology. It may be difficult to use either for making cross-technology comparisons. Finally, during the course of this study it was found that process techniques that improve the radiation hardness of MOS devices at room temperature can greatly reduce the 1/f noise of MOS devices at cryogenic temperatures.*