| Summary: | 碩士 === 國立東華大學 === 材料科學與工程學系 === 91 === The (Ba,Sr)TiO3 (BST) thin films have been recognized as the potential dielectric materials of Gbit DRAM. This work added the Pb content to the multi-doped (Ba,Sr)TiO3 to form four kinds of compositions with different Pb ratios of 0, 5%, 10%, and 20%. The purpose of this work is to deposit four kinds of multi-doped BST thin films with high permittivity by spin coating. The research of Pb-added multi-doped (Ba,Sr)TiO3 thin films was focused on the XRD structure analysis, microstructure, and dielectric and electric properties. The Pb-added multi-doped and vacuum-sintered BST bulks were also prepared for studying the effect of annealing temperature on dielectric properties and resistivity.
The results showed the Pb-free multi-doped powders crystallized to a perovskite structure after calcined at 700~800℃. The powders crystallized at lower temperature as the addition of Pb2+ increased. The 0 mol% Pb2+-doped bulk which was annealed at 1000℃ for 1 hour after vacuum sintering possessed a extremely high dielectric constant. A dielectric constant of 75,307, loss tangent of 0.095, TCC (at 145℃) of 5.2 %, and the resistivity of 3.69×107 ( Ω-cm ) were measured.
For thin films, the XRD results showed the multi-doped (Ba,Sr)TiO3 thin films have higher crystallinity at higher annealing temperatures. The microstructural analysis by FE-SEM observed the thin films with flat and dense surfaces. A dielectric constant of 510, loss tangent of 0.34, and leakage current density of 1.26×10-6 A/cm2 at 1 volt were measured for the 0.05 mol% Pb2+-doped (Ba,Sr)TiO3 thin films after annealing at 800℃ for 30 minutes.
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