Dependence of the radiation sensitivity of MOS structures on the properties of SiO2 layer

The dependence is shown of the threshold voltage shift of a MOS transistor on the oxide layer thickness, electron diffusion lengths, on the gate bias, and irradiation time. The dependence is linear for low L values, it is quadratic for high L values. For L→0 the threshold voltage shift is independent of the oxide layer thickness. The dependence of the shift on rms voltage was experimentally tested for MOS transistors with a SiO2 layer O.12 μm in thickness. The results show that it increases with the dose; saturation occurs upon further increasing the dose. (J.P.)