INFLUENCES OF THE [(BA,SR)TIO3]-MODIFIED RUO2 INTERFACE ON THE DIELECTRIC-CONSTANT AND CURRENT-VOLTAGE CHARACTERISTICS

The electrical properties of (Ba,Sr)TiO3 (BST) thin films on modified RuO2 electrodes were investigated. The surfaces of rf magnetron sputte red RuO2 electrode were modified by rf plasma etching, O-2 annealing, and overlayer coating of Pt. BST thin films were deposited on the vari ous electrodes at identical conditions. There was no significant influ ence of the surface roughness on the phase formation and columnar, hil lock-free, and dense BST films were obtained in all cases. BST films o n different electrodes showed analogous dielectric constant when the e ffective electrode area was considered in calculation. But the roughen ed surface having large charge accumulation area is advantageous for c arrying larger charge storage capacity. The leakage current of the BST film on RuO2 electrode without any modification at 1.5 V was 5.06 X 1 0(-5) and it increased to 7.92 x 10(-5) and 1.07 X 10(-4) A/cm(2) for the BST films on annealed RuO2 and rf plasma etched RuO2, respectively . The BST film on Pt/RuO2/SiO2/Si showed the lowest leakage current of 9.64 X 10(-7) A/cm(2) The Schottky barrier height acquired from the t emperature dependence of I-V characteristics turned out to be 0.94, 0. 79, 0.72, and 1.65 eV for the interface between the BST film and the R uO2 reference, rf plasma etched RuO2, annealed RuO2, and Pt(50 nm)/RuO 2. (C) 1997 American Vacuum Society.