Effects of rapid thermal annealing in vacuum on electrical properties of thin Ta2O5–Si structures

Abstract

The effect of rapid thermal annealing (RTA) in vacuum (1273K) on the properties of thin thermal Ta2O5 films in dependence on the oxidation temperature (673–873K) has been studied. It is established that the electrical and dielectric properties of the annealed layers are rather strong function of the oxidation temperature than of the film thickness. RTA reduces the leakage current of layers oxidized at 673 and 773K and deteriorates the current for layers formed at 823 and 873K—in both the cases the effect is stronger for shortest annealing time. The leakage current level after annealing of the lower-oxidation temperature layers is comparable with that of the as-grown high temperature oxidized films. The effect of RTA on the dielectric constant and fixed oxide charge is complex and there is not a simple relation with the leakage current behaviour—the annealing is not beneficial for fixed oxide charge in poorly oxidized films at 673 and 773K. The results are discussed in terms of oxidation and crystallization effects during the annealing in the oxygen free ambient and their relation with the properties of the initial Ta2O5–Si structures.