Preparation of ultra thin SrBi2Ta2O9 films using metalorganic chemical vapor deposition combined with a modified annealing method

We report a capacitor-preparation method using an ultra thin SrBi2Ta2O9 (SB T) film for application to low-voltage-operated ferroelectric random-access memories (FeRAMs). As the film thickness was reduced below 100 nm, the SET capacitor reached dielectric breakdown at a much lower electric field. Ato mic force microscopy (AFM) analysis revealed that the crystallization annea ling roughened the interface between the electrode and SET. We attributed t he electrical breakdown to the localized electric field at the roughened in terface. By modifying the annealing method for crystallization of SET, the interface was maintained smooth and flat even after the crystallization ann ealing, resulting in good performance in terms of the leakage current vs. a ppled voltage (I-V) characteristics. Employing a 50 nm thick SET film, by t he modified annealing method, a low-voltage operation as well as highly ins ulating properties was realized: the remanent polarization (2P(r)). coerciv e field (V-c) and leakage current density (J) at 1.5 V were 12.2 muC/cm(2), 0.36 V and approximately 5 x 10(-9) A/cm(2), respectively.