Ionizing radiation induced phenomena in MOS structures

A systematic experimental study of electron and gamma ray irradiation on MOS structures is presented with regard to the influence of technological parameters. The purely electronic degradation mechanisms are found to be insufficient, and the physico-chemical phenomena occurring in the presence of humid oxides are emphasized. Experimental results are correctly described when ionic exchanges between the electrodes and the oxide volume are taken into account. Thermal annealing is shown to considerably reduce the ionic degradation; the importance of this is evaluated from the degree of irreversibility of positive charge trapping. A phenomenon of negative charge trapping was established emphasizing the electronic exchanges at the oxide insulator interface. Both electronic and ionic degradations are closely related to technological parameters, the consequences of which are discussed.