Electrical properties of (Ba, Sr)TiO3 films on Ru bottom electrodes prepared by electron cyclotron resonance plasma chemical vapor deposition at extremely low temperature and rapid thermal annealing

(Ba, Sr)TiO3 (BST) films were prepared on Ru bottom electrodes by electron cyclotron resonance chemical vapor deposition at extremely low temperature and rapid thermal annealing (RTA). Leakage current characteristics were imp roved by lowering the BST deposition temperature down to 120 degrees C. (Ba +Sr)-rich films with a (Ba+Sr)/Ti ratio of 1.1-1.5 had lower leakage curren t densities than stoichiometric and Ti-rich films with a ratio of 0.8-0.9. Cross sectional transmission electron microscopy observations showed chat t he 120 degrees C-deposited and 700 degrees C-RTA-treated (Ba+Sr)-rich film had a granular structure and smooth interfaces with the electrodes. The sto ichiometric and Ti-rich films had columnar structures and larger interface roughness. As a result, low leakage current density less than 10(-7) A/cm(2 ) at +/-1 V were obtained for 30 nm-thick BST films with a (Ba+Sr)/Ti ratio of 1.1-1.5 by combination of 120 degrees C deposition and 700 degrees C RT A.