Influence of gamma 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 me thods (rf sputtering and thermal oxidation) have been investigated. It is e stablished that the irradiation degrades the characteristics of the layers in terms of dielectric constant, oxide charge and leakage current. At the s ame time the irradiation does not affect the breakdown fields significantly . The influence of radiation depends on both the dose and the initial quali ty 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 electrica lly active defects in irradiated films is associated with the oxygen vacanc ies 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 radia tion hardness of Ta2O5, which seems to be due to more a perfect layer struc ture obtained at high temperature oxygen treatment. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.