Conduction mechanisms in thin RF sputtered Ta2O5 films on Si and their dependence on O2 annealing

The effect of oxygen annealing at high temperature (873, 1123 K) on the conduction mechanism of RF sputtered Ta₂O₅ (26 nm) on Si has been investigated. It is established that the influence of oxygen treatment on the leakage current is beneficial for the films. A leakage current density as low as 10^-7 A/cm² at 1 MV/cm applied field for annealed layers has been obtained. The current reduction is considered to be due to removal of certain structural imperfections present in the initial layers. The conduction mechanism of the as-deposited films is found to be of Poole-Frenkel type and a change of the conduction mechanism for the annealed films at medium fields (0.8-1.3 MV/cm) is established. It is concluded that the dominant conduction mechanism in the intermediate fields can be effectively controlled by appropriate technological steps.