Abstract
We have investigated (Ba,Sr)TiO 3 (BST) films grown on Ru by a liquid source chemical vapor deposition (CVD). Inductively coupled plasma mass spectrometry (ICP-MS) analysis revealed the decline of (Ba+Sr)/Ti molar ratio of the initial BST-layer on Ru. By readjusting the flow ratio of the liquid sources and using a two-step deposition method, we obtained 30-nm-thick BST films with a uniform composition profile and exhibiting good electrical properties. The leakage property, however, was severely deteriorated in BST films less than 24 nm thick. Scanning electron microscopy observation showed the presence of micro-roughness or micro-hillocks in these films. An annealing process of the Ru electrode was added for its planarization, and the CVD process was also improved to suppress oxidation of Ru. As a result, we obtained smooth and finely crystallized ∼20-nm-thick BST films with good electrical properties at an equivalent SiO 2 thickness ( t eq) of ∼0.45 nm and leakage current <1×10 −7 A/cm 2. We also measured the properties of BST films deposited on the three-dimensional Ru electrode.
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