Plasma-enhanced atomic layer deposition of barium titanate with aluminum incorporation

Plasma-enhanced atomic layer deposition (PEALD) of ultrathin (∼7 nm) slightly Ti-rich Ba_xTi_yO_z (BTO) films with different Al-doping concentration ([Al]/([Al] + [Ba] + [Ti]) = 0 to 22 at%) was studied. In particular, the effects of Al-doping in BTO on compositional, crystallographic and electrical properties were investigated. Previously, BTO films with a Ti cation composition, [Ti]/([Ba] + [Ti]) = ∼60 at% was reported to be advantageous for crystallization, resulting in superior dielectric properties. These Ti-rich BTO films, however, suffered from high leakage currents, necessitating the change in its crystalline structure as well as elemental composition. By incorporating Al₂O₃ into the BTO films, the leakage current can be controlled, where the BTO films with an Al-doping concentration of 12 at% showed a leakage current reduced by one order of magnitude compared to un-doped BTO (i.e., ∼10⁻⁷ to ∼10⁻⁶ A/cm² at +1.6 V) without a significant drop of the dielectric constant (43,un-doped to 40, Al-doped).