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

Plasma-enhanced atomic layer deposition (PEALD) of ultrathin (∼7 nm) slightly Ti-rich BaxTiyOz (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).