High-dielectric Ba0.5Sr0.5TiO3 (BST) thin films are grown on Ir and Ir
O2 electrodes by a rf sputtering method. The structural and electrical
properties of BST films are investigated. After postannealing at 750
degrees C for 30 min in N-2 atmosphere, the interface between BST and
IrO2 remains flat and the IrO2 does not show any structural change. On
the other hand, a thin IrO2 layer is formed at the interface between
the BST and Ir after the same post-annealing. A larger grain size of B
ST film is obtained on the Ir electrode compared to that of BST him on
the IrO2 electrode. Dielectric constants of 36-nm-thick BST films on
Ir and IrO2 are 338 and 290, respectively. The leakage current densiti
es of both the Pt/BST/Ir and Pt/BST/IrO2 capacitors are about 20 nA/cm
(2) at +/-1.5V, which is sufficiently small for application to dynamic
random access memory devices.