Effect of bottom electrodes on resistance degradation and breakdown of (Ba, Sr)TiO3 thin films

The influence of bottom electrodes (Pt, Ir, Ru) on the degradation of (Ba,S r)TiO3 (BST) thin films under dc stress conditions was investigated. The cu rrent-time (I-t) end current-voltage (I-V) measurement results indicated th at the BST thin films deposited on Ru have faster degradation than those de posited on Pt and Ir. The degradation was considered to be caused by the de terioration of Schottky-barrier. Under de stress conditions, the dielectric relaxation current in the BST dielectric films probably enhances the deter ioration. The breakdown time was found to be approximated by an exponential function of an electric field [t(B) = alpha exp(-beta E)] for dc stress. T he value of the exponential factor beta for BST deposited on Pt and Ir was about a quarter of that for BST deposited on Ru. The different value of bet a observed under de stress indicates that the degradation of BST on Ru woul d be more serious than on Pt and Ir. The ten Sears lifetime of time-depende nt dielectric breakdown (TDDB) studies indicate that BST on Pt, Ir and Ru h ave longer lifetime over ten years on operation at the voltage bias of 1 V.