Influence of γ radiation on thin Ta2O5-Si structures

The effect of gamma irradiation (10(6)-5 x 10(7) rad) on the electrical and dielectric properties of thin tantalum pentoxide layers obtained by two methods (rf sputtering and thermal oxidation) have been investigated. It is established that the irradiation degrades the characteristics of the layers in terms of dielectric constant, oxide charge and leakage current. At the same time the irradiation does not affect the breakdown fields significantly. The influence of radiation depends on both the dose and the initial quality of the layers including their thickness: the degradation is more severe for the higher dose and the thinner layers; the as-fabricated, non-annealed films show poor immunity to radiation damage. The main source of electrically active defects in irradiated films is associated with the oxygen vacancies and the broken Ta-O and Si-O bonds. It was established that the higher temperature oxidation or annealing in O-2 are more beneficial for the radiation hardness of Ta2O5, which seems to be due to more a perfect layer structure obtained at high temperature oxygen treatment. (C) 2001 Elsevier Science Ltd. All rights reserved.