Improvement in structural and dielectric properties of sputtered Ta₂O₅ thin film by post-deposition annealing

In current years, the growth of high-k dielectric thin films with reduced charge density and leakage current has drawn tremendous attention for microelectronic devices. Ta₂O₅ thin film is deposited on p-type silicon substrate using radio frequency sputtering deposition technique for high-k dielectric applications. The as-deposited films undergo post-deposition annealing treatment at temperatures ranging from 600 °C to 900 °C for 1 h in air ambient. X-ray diffraction analysis revealed the formation of a polycrystalline orthorhombic β – Ta₂O₅ structure in the annealed films. The RMS roughness of the film is found to be increased from 2.3 nm to 3.7 nm with the increase in annealing temperature to 900 °C. Metal–oxide–semiconductor (Al/Ta₂O₅/p-Si) structures are fabricated using thermal evaporation for electrical characterizations. The capacitance-voltage (at 1 MHz) of this structure is measured for the sweep voltage from − 4 V to + 4 V. The oxide charge density and interface charge density of the film have been calculated from the C-V curve and found to decrease with the increase in annealing temperature. The highest dielectric constant value of 24.5 at 1 MHz is found for film annealed at 800 °C. The leakage current is measured from the current-voltage measurement and found to be minimum for the film annealed at 800 °C.