Radiation effects in TaSix/polysilicon MOS gate structures

Silicide deposition methods, contamination of underlying oxide layers, and the use of high temperatures to crystallize the films are discussed in relation to their effects on radiation hardness. Large dose enhancement effects for photon energies ≲300 keV are predicted for MOS devices using TaSix/polysilicon gate electrodes. However, experiments at 15, 100, and 1000 keV show no large differences in threshold voltage shifts among MOS capacitors using Al/poly, TaSix/poly, and W/poly gates. Among devices using various gate materials, differences in the amount of interface state generation and hole trapping within the gate oxide after irradiation are attributed to differences in the amount of mechanical stress in the oxide layers.