Cation composition control of MOCVD (Ba,Sr) TiO3 thin films along the capacitor hole

The variations in the cation concentration ratio of metallorganic chemically vapor deposited (MOCVD) (Ba, Sr) TiO3 (BSTO) and SrTiO3 (STO) thin films along a capacitor hole with a diameter of 0.15 mum were investigated. Even under deposition conditions that would produce cation-stoichiometric films on a nonpatterned wafer, the (Ba + Sr)/Ti and Sr/Ti ratios varied remarkably along the depth direction of the hole when the usual shower-head-type chemical vapor deposition chambers were used. The Sr/Ti ratios increased or decreased depending on the wafer temperature, the flow rate, and the types of precursors. When a new dome-type chamber was adopted and the dome temperature was 450degreesC, completely conformal composition and thickness step coverages were obtained at a wafer temperature of 420degreesC on the 0.15 mum capacitor hole pattern. The variation in the composition and thickness step coverages were interpreted in terms of the variation in the sticking coefficients of the precursors according to the various deposition conditions and types of precursors and chambers. (C) 2002 The Electrochemical Society.