Ferroelectric strontium bismuth tantalate thin films deposited by metalorganic chemical vapour deposition (MOCVD)

Abstract Thin films of Sr 1− x Bi 2+ x Ta 2 O 9 (SBT) have been deposited by metalorganic chemical vapor deposition (MOCVD) on 150 mm Si wafers with Pt/Ti electrodes. The choice of Bi precursor significantly affects the process; film homogeneity is significantly improved when using a β-diketonate Bi precursor in combination with compatible Sr and Ta precursors. A highly repeatable process has been developed, with good run-to-run composition and thickness control. Effects of Bi volatility have been investigated in annealing experiments that show the onset of Bi loss at ∼570°C at reduced pressure (1–10 Torr). Film properties relevant to integrated ferroelectric random access (Fe RAMS) memories have also been characterized. Remenant polarizations (2 P r ) up to 24 μC cm −2 have been obtained at 5 V, with 90% saturation of 2 P r at 1·5 V and a coercive voltage of 0·52 V for a 140 mn film. Electrical leakage current density values were −8  A cm −2 at 1·5 V. Fatigue endurance has been measured to 10 11 cycles with