Combined effects of hot-carrier stressing and ionizing radiation in SiO/sub 2/, NO, and ONO MOSFETs

N-channel MOSFETs with different gate dielectrics, such as silicon dioxide, silicon dioxide annealed in nitrous oxide (NO), and reoxidized nitrided oxide (ONO), were first hot-carrier (HC) stressed and then irradiated to a total dose of 1.5 Mrd. For equal substrate current stressing NO devices have the least degradation, whereas the threshold voltage (V/sub t/) shift due to irradiation is maximum for these devices. For all three types of gate dielectrics the V/sub t/ shift due to irradiation of HC stressed devices was higher than that of the unstressed device. However, for ONO devices the V/sub t/ shift due to irradiation of the hot-electron stressed (stressing with V/sub d/=V/sub g/=6.5 V) device was less than that of the unstressed device.<
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