Radiation-Induced Oxide Charge in Low- and High-H2 Environments

Electronic structure calculations and irradiation measurements are used to obtain insight into oxide trapped charge mechanisms in varying hydrogen ambients. Quantitative agreement between measured and simulated oxide and interface-trap charge densities is obtained over a wide range of H-2 concentrations by implementing first-principles calculations of the energetics, and dynamics of charge transport and trapping, into TCAD simulations of irradiated MOS structures. Hole trapping dominates for typical H-2 densities, but protons can dominate at high H-2 densities. The rate of the interface trap reaction, in which protons that are liberated from charged oxygen vacancies by molecular hydrogen form dangling bonds on the interface, is found to play a key role in determining the relative concentrations of oxide and interface-trap charge densities.