Influence of the substrate bias voltage on the physical properties of dc reactive sputtered Ta2O5 films

Abstract

Tantalum oxide (Ta2O5) films were deposited on ITO glass substrates by dc reactive magnetron sputtering in oxygen/argon gas mixture. The performance of Ta2O5 films deposited at different substrate bias voltages in the range from 0 to −145V was investigated in detail. Our results show a decrease both in the film porosity and the surface roughness as the substrate bias voltage changes within a certain scope, which interestingly leads to a conspicuous improvement of their electrical properties. Further increasing of the negative bias voltage, however, results in deterioration of the film packing density, surface morphology, and leakage current as well. Under the optimal substrate biasing condition (−135V), the Ta2O5 films exhibit attractive electrical properties, namely a permittivity value as high as ∼23, a dielectric loss of ∼0.01, and a leakage current density as low as 1.45×10−7A/cm2 at 1MV/cm.