Radiation-induced oxide charge in low-and high-h ₂ 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.