Effects of switched gate bias on radiation-induced interface trap formation [MOS transistors]

Switched gate bias experiments were used to test the hydrogen model for the time-dependent buildup of interface traps n_it after a radiation pulse. In the hydrogen model, slow transport of radiation-induced H⁺ ions through the oxide to the Si/SiO₂ interface is the rate-limiting step in the n_it formation process. A model based on dispersive transport theory was used to numerically simulate the time-dependent H⁺ drift through the oxide toward the gate under negative bias, then back toward the Si/SiO₂ interface under positive bias. Good agreement between the simulations and experiment is obtained for the final magnitude of ΔN_it, both for positive and negative bias during irradiation. The procedure used for the numerical simulations provides only a lower bound on the transport time when the direction of the gate bias is switched during the N_it buildup. This behavior is due to a memory effect in the dispersive H⁺ transport