Low leakage current BaTiO₃ thin film capacitors using a multilayer construction

Innovative device designs were used to fabricate low leakage ferroelectric BaTiO₃ (BTO) thin film capacitors. BTO thin films with thicknesses ranging from 220 nm to 265 nm were deposited using reactive r.f. magnetron sputtering. A highly stable and conductive metallic oxide, RuO₂, was used as the bottom electrode of the capacitors on SiO₂ Si substrates. Layers of BTO deposited at low temperature were amorphous and those deposited at high temperature above 600 °C were polycrystalline. Microcrystallization of amorphous BTO took place at a thermal treatment temperature of above 600 °C. Capacitors with a bilayer configuration of polycrystalline layers on microcrystalline layers showed a capacitance per unit area of around 2.4 × 10⁵pF cm^-2 and a leakage current density of (8.5 ± 0.5) × 10 ^-8A cm ^-2 at a field intensity of 2 × 10⁵V cm ^-1. A capacitance per unit area of around 1.4 × 10⁵ pF cm ^-2 and a leakage current density of around 10^-10A cm^-2at a field intensity of 2 × 10⁵V cm ^-1 were achieved on the capacitors with a nanolayer configuration of amorphous layers on a number of stacked cycles of polycrystalline layers on microcrystalline layers.