Permanent Radiation Effects in Complementary-Symmetry MOS Integrated Circuits

The predominant effect of radiation on a typical metal-oxidesemiconductor (MOS) transistor is a shift in the threshold or "cut-off" voltage of the device. Since these devices are in other respects extremely well suited to space applications, the problem of estimating and accommodating the anticipated threshold voltage shift has been examined. This paper presents guidelines which will assist the designer to predict the limits within which the values of these changes will fall. These predictions are based on extensive tests of complementary-symmetry MOS devices, as well as the more conventional MOS transistors and integrated circuits. A parallel research program has provided a better understanding of the damage effects. The first part of the paper presents the results of radiation-testing a wide variety of MOS devices that canbe used for estimating the anticipated threshold voltage shift at various dose levels. The second part of the paper presents data on the behavior of MOS devices when gate bias during irradiation is applied intermittently instead of continuously.