Apparent dopant concentration reduction on MOS capacitors after high doses of ionizing radiation

The apparent dopant concentration reduction near the interface of Metal-Oxide-Semiconductor (MOS) capacitors has been studied after exposure to ionizing radiation with dosages of up to 500 Mrad (Si). The effect and its characteristics are analyzed as a function of device size, total dose, initial damage level, and time evolution. The dependence of dopant reduction with ionizing radiation dosage indicate a behavior in the form Delta N/No similar to(dose)(alpha), where 1/2 less than or equal to alpha less than or equal to 1 after a least square fitting to the power law. The range for possible values of ct depends on processing parameters and device history prior to irradiation. The experimental results suggest a correlation between the dopant reduction and the densities of oxide charge and interface traps generated by the ionizing radiation and their behavior during and after the irradiation.