Atomic layer deposited Ta2O5: From process optimization to thin film characterization

Abstract

Tantalum pentoxide (Ta2O5) thin films were grown by atomic layer deposition (ALD) using pentakis(dimethylamino)tantalum (PDMAT) and H2O at temperatures between 150 and 300 °C. A peak growth rate of 0.68 Å/cycle was achieved at 200 °C. The as-deposited films from the optimal process are oxygen rich with an oxygen-to-tantalum (O/Ta) ratio of 3.3. Various thin film characterization methods were undertaken, and they showed that the as-deposited Ta2O5 films are amorphous and have a large optical bandgap of 4.1 eV. They possess a high breakdown strength of 3.9 MV cm−1, a high electrical resistivity of 1 × 1013 Ω cm, and a respectable dielectric constant of 14, indicating its suitability as high k dielectric materials in optical and electronic devices. Moreover, a phase transition to polycrystalline β-Ta2O5 occurs after annealing at 700 °C, and it is stable up to 1000 °C.