Thin films of layered-structure (1 - X)SrBi2Ta2O9-XBi3Ti(Ta1-yNb y)O9 solid solution for ferroelectric random access memory devices

Abstract

We report on the thin films of solid-solution material (1-x)SrBi2Ta2O9-xBi3Ti(Ta 1-yNby)O9 fabricated by a modified metalorganic solution deposition technique for ferroelectric random access memory devices. Using the modified technique, it was possible to obtain the pyrochlore free crystalline thin films at an annealing temperature as low as 600 °C. The solid-solution of layered perovskite materials helped us to significantly improve the ferroelectric properties, higher Pr and higher Tc, compared to SrBi2Ta2O9; a leading candidate material for memory applications. For example, the films with 0.7 SrBi2Ta2O9-0.3Bi3TiTaO9 composition and annealed in the temperature range 650-750 °C exhibited 2Pr and Ec values in the range 12.4-27.8 μC/cm2 and 68-80 kV/cm, respectively. The leakage current density was lower than 10-8 A/cm2 at an applied electric field of 200 kV/cm. The films exhibited good fatigue characteristics under bipolar stressing. © 1997 American Institute of Physics.