Chemical vapor deposition of barium strontium titanate thin films using direct liquid injection of a single cocktail solution with Ba(methd)2, Sr(methd)2, and Ti(MPD)(tmhd)2

Abstract

Deposition characteristics of (Ba,Sr)TiO3 (BST) thin films by metalorganic chemical vapor deposition with a mixture solution were investigated. Ba(methd)2 (methd = methoxyethoxytetramethylheptanedionate), Sr(methd)2, and Ti(MPD)2(tmhd)2 (MPD = methylpentanedioxy, tmhd = tetramethylheptanedionate) were dissolved together in methanol solvent. Mass spectrometry showed that Ba(methd)2 was less aggregated than Ba(tmhd)2-tetraglyme adduct (tetraglyme = tetraethylene glycol dimethyl ether) in the gas phase. Similar results were obtained from Sr precursors. Step coverage and electrical properties of the BST films were investigated as a function of deposition temperature from 350 to 600 °C. With the increase of the deposition temperature up to 500 °C, Ti composition in the films was increased, but Ba and Sr remained almost constant, and the step coverage became poor. Also, leakage current density and SiO2 equivalent oxide thickness was reduced as the deposition temperature increased. Poor incorporation of Ti below the deposition temperature of 500 °C was observed.