Interface states in r f sputtered Ta2O5 films on silicon

Interface state densities of metal-insulator-silicon (MIS) structures containing r f sputtered Ta2O5 insulating films 30 to 50 nm thick, both as grown and oxygen annealed, with different gate metals (Al, W and Au), were studied by using the results from high frequency and quasi-static C-V measurements.It was found that the optimum value of the high frequency to be used is 100 khz, and the determination of the interface state densities was done at the frequency. The interface state density at mid gap (Ditm) both for as grown and for oxygen annealed Ta2O5 was essentially the same. No significant difference is observed for the MIS structures with different gate metals. These findings suggest that for the r f deposited Ta2O5 insulating films thicker than 30 nm nor the oxygen annealing neither the gate deposition step influence the typically interfacial properties as are the interface state densities, although the bulk properties as well as the oxide charges densities are significantly changed. (Author)