Analysis of the Resistance Degradation of SrTiO₃ and Ba_xSr_(1-x)TiO₃ Thin Films

Abstract

For bulk SrTiO 3 (ST), it is known that the leakage current increases abruptly at a certain time under a constant bias (resistance degradation). We investigated the resistance degradation of ST and Ba x Sr (1- x ) TiO 3 (BST) thin films because it will be a reliability problem when these thin films are applied to DRAM cell capacitors or on-chip capacitors. The 1000-Å-thick ST or BST was sputter-deposited in situ on an electron-beam-evaporated Pt bottom electrode. The I-t and I-V characteristics were measured for these films with thermally evaporated Au top electrodes. For positive bias on the top electrode, the films showed resistance degradation similar to that of bulk single-crystal ST. However no degradation was found for negative bias. The I-V characteristics showed that only the electric field enhancement at the bottom interface does not account for this polarity dependence of the resistance degradation. A possible explanation is intrinsic inhomogeneous distribution of oxygen vacancies in the films.