Effect of annealing on dielectric dispersion of tantalum oxide films prepared by RF sputtering

Effect of annealing in oxygen and argon mixtures during the RF sputtering process on the dielectric dispersion of tantalum oxide films are investigated as a function of the film thickness and annealing temperature. Dielectric properties of thin tantalum oxide films prepared at room temperature show anomalous dielectric dispersion in the low frequency range. Very high dielectric constant and dielectric loss are observed in the frequency of 10-10 kHz. The frequency of dielectric loss peak increased with the increment of measuring temperatures and this peak shows strong thickness dependence. These characteristics are explained in terms of interfacial polarization between the aluminum and tantalum oxide layer based on the Maxwell-Wagner mechanism. It is shown that these anomalous dielectric dispersion are drastically improved by increasing annealing temperature and no dielectric loss peaks are observed for the film prepared at 400°C. It is also shown that the leakage current in a low voltage region are reduced to less than 1/10 by annealing at a temperature of 400°C