Time dependence of interface trap formation in MOSFETs following pulsed irradiation

The time dependence of interference trap (N_it) formation in MOSFETs was studied as a function of gate oxide thickness, oxide growth type, substrate orientation, temperature, and gate bias. Two different N_it formation mechanisms are observed. Most (typically 90%) of the formation, called the late process, occurs slowly at long times (1-10000 s) after the radiation pulse. From a variety of experimental data, it is concluded that the rate of the late process is limited by drift of a radiation-induced positive ion, probably H⁺ , through the gate oxide to the Si-SiO₂ interface where the N_it are formed. A relatively fast, or early, process is responsible for a small percentage of the total N_it formation. The time constant for this process appears to be consistent with hole drift through the oxide