Influence of substrate temperature on the structural, dielectric and optical properties of RF magnetron sputtered Ta2O5 films

Tantalum oxide (Ta2O5) films were deposited on p-silicon and quartz substrates by sputtering of pure tantalum target in the presence of reactive and sputter gases of oxygen and argon at various substrate temperatures in the 303 - 973 K range employing RF magnetron sputtering technique. The effect of substrate temperature on the chemical binding configuration, crystallographic structure, dielectric and optical properties of the Ta2O5 films was studied. X-ray photoelectron spectroscopic studies revealed that the oxidation of the films increased with the increase of substrate temperature. X-ray diffraction studies indicated that the films deposited at substrate temperatures >= 673 K were orthorhombic beta- phase Ta2O5. The dielectric constant of the p-Si/Ta2O5/Al structure increased from 14 to 21 with the increase of substrate temperature from 303 to 973 K. Optical band gap of the films decreased from 4.47 to 4.26 eV and refractive index increased from 1.82 to 2.19 with the increase of substrate temperature from 303 to 973 K respectively.