Leakage current properties of Ba0.7Sr0.3TiO3 thin films depending on the film thickness

High permittivity materials such as Ba_0.7Sr_0.3TiO₃ (BST) have attracted much attention as thin film materials for capacitors in further DRAM generations. Of particular interest are not only the dielectric constant but also the leakage current. Therefore the leakage current properties of BST were investigated as a function of the film thickness and the temperature. BST thin films were prepared by using chemical solution deposition (CSD) on platinum bottom electrodes in a thickness range from 26 nm up to 310 nm. To obtain a capacitor structure Pt top electrodes were sputtered on top of the BST. A result of this work is that the leakage current properties of thin films improve with decreasing thickness (at a constant electric field). For an estimation of the barrier height the leakage current properties were measured at different temperatures in a range from room temperature up to 600 K. From these measurements the barrier height can be estimated.