EFFECT OF BARRIER LAYERS ON BATIO3, THIN-FILM CAPACITORS ON SI SUBSTRATES

The choice of the bottom electrode or barrier layer plays an important role in determining the electrical and structural properties of metal/ferroelectric/metal thin film capacitors. A substantial improvement of the electrical and structural properties of the capacitors was found by using RuO2 as a bottom electrode. Electrical measurement on a capacitor with a structure of BaTiO3(246 nm)/RuO2 (200 nm)/SiO2/Si, where the BaTiO3 thin film was deposited at room temperature, showed a dielectric constant of around 15, leakage current density of 1.6 x 10(-7)A/cm(2) at 4 V, a de conductivity of 9.8 x 10(14)S/cm, and a capacitance per unit area of 5.6 x 10(4) pF/cm(2). A similar structure but with polycrystalline BaTiO3 (273 nm) as the dielectric deposited at 680 degrees C showed a dielectric constant of 290, leakage current density of 1.7 x 10(-3)A/cm(2) at 4 V, a de conductivity of 1.2 x 10(-8) S/cm, and a capacitance per unit area of 9.4 x 10(5) pF/cm(2). Scanning electron microscopy analysis on the films showed differences in the microstructure due to the use of different bottom electrode materials, such as RuO2 or Pd.