Low temperature processed 0.7SrBi2Ta2O9–0.3Bi3TaTiO9 thin films fabricated on multilayer electrode-barrier structure for high-density ferroelectric memories

Abstract

Thin films of solid-solution material 0.7SrBi2Ta2O9–0.3Bi3TaTiO9 (0.7SBT–0.3BTT) were fabricated on n+-polycrystalline (n+-poly) Si substrates by a metalorganic solution deposition technique at a low processing temperature of 650 °C using a Pt–Rh/Pt–Rh–Ox electrode-barrier structure. The Pt–Rh/Pt–Rh–Ox structure was deposited using an in situ reactive radio frequency sputtering process. The electrodes had a smooth and fine-grained microstructure and were excellent diffusion barriers between the 0.7SBT–0.3BTT thin film and Si substrate. The ferroelectric (0.7SBT–0.3BTT) test capacitors using these electrode-barrier grown directly on Si showed good ferroelectric hysteresis properties, measured through n+-poly Si substrate, with 2Pr and Ec values of 11.5 μC/cm2 and 80 kV/cm, respectively, at an applied electric field of 200 kV/cm. The films exhibited good fatigue characteristics (<10% decay) under bipolar stressing up to 1011 switching cycles and the leakage current density was lower 10−7 A/cm2 at an applied electric field of 200 kV/cm. The good ferroelectric properties of 0.7SBT–0.3BTT solid-solution thin films at a low processing temperature of 650 °C and excellent electrode-diffusion barrier properties of a Pt–Rh/Pt–Rh–Ox structure are encouraging for the realization of high-density nonvolatile ferroelectric random access memories on silicon substrates.