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/sub it/ after a radiation pulse. In the hydrogen model, slow transport of radiation-induced H/sup +/ ions through the oxide to the Si/SiO/sub 2/ interface is the rate-limiting step in the n/sub it/ formation process. A model based on dispersive transport theory was used to numerically simulate the time-dependent H/sup +/ drift through the oxide toward the gate under negative bias, then back toward the Si/SiO/sub 2/ interface under positive bias. Good agreement between the simulations and experiment is obtained for the final magnitude of Delta N/sub 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/sub it/ buildup. This behavior is due to a memory effect in the dispersive H/sup +/ transport.<
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