Gamma-Radiation Effects in CMOS Transistors

Effects of gamma-radiation in Al-gate and Si-gate CMOS transistors have been investigated in this paper. It has been found that, besides the well-known threshold voltage instabilities, radiation causes the gain factor instabilities as well. These instabilities of CMOS transistor electrical parameters have been found to be caused by significant increase of positive gate oxide charge density and somewhat smaller increase of interface trap density. While the positive gate oxide charge increase has been explained in terms of the broken bond model, a new model has been proposed to elucidate the interface trap increase as well as existing partial compensation of the created positive gate oxide charge. Finally, note that no significant difference in radiation hardness between Al-gate and Si-gate CMOS transistors has been observed.