Si-SiO2 interface state generation during X-ray irradiation and during post-irradiation exposure to a hydrogen ambient [MOSFET]

The changes in the number of interface traps and oxide traps which result when a previously X-ray irradiated MOSFET is exposed to a hydrogen ambient were measured. At room temperature, a doubling in the number of positively charged oxide traps was observed. The increase in the number of interface states is approximately the same as the decrease in the number of oxide traps. These changes could result from the cracking of H₂ by positively charged radiation-induced defects in the oxide. This cracking reaction produces H⁺ ions which are then transported to the interface (under positive gate bias), where they react to form interface states. The necessity of positively charged radiation-induced defects in the oxide to explain the postirradiation buildup of interface states leads to the proposal of a model for the buildup of interface states during and immediately after irradiation. This model supports recent models of interface state formation as resulting from H⁺ transport and clarifies the origin of the H⁺