Barium strontium titanate, $(Ba,Sr)TiO_3(BST)$, thin films were prepared on Pt-base electrodes($Pt(111)/SiO_2/Si(100)$) and bare Si(100) by liquid source misted chemical vapor deposition(LSMCVD), where barium bis(dipivaloylmethanate) [$Ba(dpm)_2, Ba(C_{11}H_{19}O_2)_2$], strontium bis(dipivaloylmethanate) [$Sr(dpm)_2, Sr(C_{11}H_{19}O_2)_2$] and titanium tetraisopropoxide [$Ti(OC_3H_7^i )_4$] were used as Ba, Sr and Ti sources, respectively. Effects of heat treatment, modification of Pt-base electrode, and solvent on film properties, such as crystallinity, surface morphology, elemental composition, chemical bonds of elements, and electrical characteristics, were investigated in order to prepare BST thin films with perovskite phase at lower annealing temperature, and electrical characteristics applicable to DRAM.
BST thin films baked above 450℃ and annealed above 650℃ had the perovskite phase with (110) orientation. FTIR showed that organic residues disappeared above 650℃. BST thin film baked at 450℃ and annealed at 750℃ had a dielectric constant of 221 and a dissipation factor of 0.10 at 100kHz, respectively. The leakage current density was $8.29×10^{-6}A/㎠$ at 1.5V. Crystallization temperature of BST thin films was lowered by using metal dpm compounds, but the films had lower dielectric constants than those by other precursors or processes.
$Pt/SiO_2/Si$ was heated at 100℃ under $O_2$ atmosphere, and the film deposited on this substrate had a dielectric constant of 139, a dissipation factor of 0.05 at 100kHz, respectively, and a leakage current density of $3.63×10^{-7}A/㎠ at 1.5V, which is lower than those of the films on bare $Pt/SiO_2/Si$.
BST thin film prepared by using THF had little perovskite phase due to organic residues which disappeared above 800℃. The film had a dielectric constant of 126, a dissipation factor of 0.15 at 100kHz, respectively, and a leakage current density of $2.58×10^{-5}A/㎠$ at 1.5V, which are higher than those of the films prepared by using 1-butanol.
