Improvement of interfacial and dielectric properties of sputtered Ta2O5 thin films by substrate biasing and the underlying mechanism

The use of tantalum pentoxide (Ta2O5) thin films as advanced gate dielectrics in integrated circuits has been hampered by thermodynamic instability at the Ta2O5/Si interface. We have demonstrated the fabrication of crystalline Ta2O5 thin films on n-type Si (100) at lower substrate temperature by means of substrate biasing. In the work reported here, the influence of the substrate bias on the interfacial and dielectric characteristics of the Ta2O5 thin films is investigated in details. Our results show that by applying a suitable bias to the Si substrate, the dielectric properties of Ta2O5 thin films can be improved. Using a substrate bias of −200 V, the thin film has a permittivity of 34 and leakage current density of 10−7A∕cm2 at an electric field of 800 kV/cm. The effects and mechanism of the bias on the interfacial and dielectric characteristics are described.