Dielectric properties of Ta2O5 thin films deposited onto Ti and TiO2 layer

The present study describes the dielectric properties of RF sputtered Ta2O5 thin films as a function of the buffer layer and annealing condition. The buffer layers were Ti or TiO2. And the thin film was annealed in various conditions. The X-ray pattern results showed that the phase of the RF sputtered Ta2O5 thin films was amorphous and this state was kept stable to RTA (rapid thermal annealing) even at 700degreesC. Measurements of the electrical and dielectric properties of the reactive sputtered Ta2O5 fabricated in two simple metal insulator semiconductor (MIS) structures, (Cu/Ta2O5/Ti/Si/Cu and Cu/Ta2O5/TiO2 /Si/Cu) indicated that the amorphous Ta2O5 grown on Ti possesses a high dielectric constant (30similar to70) and high leakage current (10(-1)similar to10(-4)A/cm(2)), whereas a relatively low dielectric constant (similar to10) and low leakage current (similar to10(-10)A/cm(2)) were observed in the amorphous Ta2O5 deposited on the TiO2 buffer layer. In addition, the leakage current mechanisms of the two amorphous Ta2O5 thin films were investigated by plotting the relation of current density (J) vs. applied electric field (E). The Ta2O5/Ti film exhibited three dominant conduction mechanism regimes contributed by the Ohmic emission at low electrical field, by the Schottky emission at intermediate field and by the Poole-Frenkel emission at high field. In the case of Ta2O5/TiO2 film, the two conduction mechanisms, the Ohmic and Schottky emissions, governed the leakage current density behavior. The conduction mechanisms at various electric fields applied were related to the diffusion of Ta, Ti and 0, followed by the creation of vacancies, in the rapid thermal treated capacitors.