Effect of barrier layers on BaTiO3 thin film capacitors on Si substrates

Abstract

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 × 10−7A/cm2 at 4 V, a dc conductivity of 9.8 × 1014S/cm, and a capacitance per unit area of 5.6 × 104pF/cm2. A similar structure but with polycrystalline BaTiO3 (273 nm) as the dielectric deposited at 680°C showed a dielectric constant of 290, leakage current density of 1.7 × 10−3A/cm2 at 4 V, a dc conductivity of 1.2 × 10−8 S/cm, and a capacitance per unit area of 9.4 × 105 pF/cm2. 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.