ELECTRICAL AND MICROSTRUCTURAL DEGRADATION WITH DECREASING THICKNESS OF (BA, SR)TIO3 THIN-FILMS DEPOSITED BY RF MAGNETRON SPUTTERING

The electrical degradation of (Ba,Sr)TiO3[BST] thin films as a functio n of the film thickness was investigated. BST thin films with various thickness were deposited on Pt/Ti/SiO2/Si substrates by in-situ RF mag netron sputtering. It was found that the electrical properties degrade d markedly as the thickness of the films decreased. Electrical propert ies such as the leakage current and the dielectric constant are closel y related to the surface morphology, in particular, the grain size of the films. The existence of an interfacial layer between the BST film and the Pt bottom electrode was confirmed by HRTEM. The interfacial la yer appeared to have crystallinity different from both the BST thin fi lm and the Pt bottom electrode which resulted in variation of the inte rfacial states between BST and Pt. As the thickness of the BST films d ecreased from 300 nm to 50 nm, the thickness of the interfacial layer increased from 9.5 nm to 11 nm. The dielectric constant of the interfa cial layer calculated from its measured overall capacitance and thickn ess, confirmed by HRTEM, was about 30. This low-dielectric-constant in terfacial layer has been shown to affect the electrical degradation of BST thin films with decreasing thickness.