The Effect of the Ionizing Radiation Intensity on the Response of MOS Structures

Abstract

The effect of the intensity of ionizing radiation on the volume charge and surface-state density of metal—oxide—semiconductor (MOS) structures with thin gate silicon dioxide is modeled. It is shown that the dependences of the surface-state density and volume charge on the total time of ionizing radiation and subsequent annealing at different ionizing-radiation intensities lie on the corresponding common curves Nit(t) and Qot(t). The Nit(t) common curve is determined by the dispersive nature of the transport of hydrogen ions Н+. The observed deviations from this Nit(t) common curve immediately after the end of ionizing irradiation are due to the transient process of the redistribution of Н+ ions. The Qot(t) common curve is determined by relaxation of the volume charge from a system of levels with energies of 0.3 to 1.0 eV by the mechanism of thermal emission. It is shown that the enhanced low-dose-rate sensitivity (ELDRS) for the MOS structures with a thick base oxide at low intensities is determined by the dispersive character of the transport of hydrogen ions Н+.