Low energy electron-excited nanoscale luminescence: a tool to detect trap activation by ionizing radiation

Ultra-thin SiO₂/Si gate dielectric structures exposed to heavy X-ray irradiation exhibit optical emission characteristic of interface traps. Low energy electron-excited luminescence spectroscopy with nanometer-scale depth resolution yields a characteristic spectral energy and excitation depth dependence. Ultra-thin (5 nm) oxide films on Si substrates exposed to 10 keV, 7.6 Mrad(SiO₂) [13.7 Mrad (Si)] X-ray irradiation introduces trap densities on the order of 10¹¹ cm^-2 ev^-1, localized near the intimate SiO₂-Si interface. This density is consistent with the trapped oxide and interface charge densities expected based on observed capacitance-voltages shifts of thicker oxides, their corresponding charge densities, and the proportionally smaller charge densities expected for the thinner oxide layers in this study