Dose-Rate Dependence of Ionizing Radiation Damage in Silicon Transistors*

The primary effects of ionizing radiation on silicon transistors is caused by the effects of electrons and holes created in the oxide portions of these devices. The holes can become trapped in the oxide, and they also create traps at the semiconductor-silicon interface. In the best- accepted explanation, the holes release hydrogen from source sites, often near the interface, and this hydrogen causes the interface traps by reacting with hydrogen-passivated Si dangling bonds at the interface. In this presentation, the transient electrical effects in a silicon device will be computed as a function of radiation duration, total dose, oxide defects, silicon doping and other physical variables. These calculations reveal mechanisms, such as bimolecular defect reactions, that make the damage dependent on the radiation dose rate if the total radiation dose exceeds a threshold dose.