Nanoscale Characterization of TiO₂ Films Grown by Atomic Layer Deposition on RuO₂ Electrodes

Topography and leakage current maps of TiO₂ films grown by atomic layer deposition on RuO₂ electrodes using either a TiCl₄ or a Ti­(O-i-C₃H₇)₄ precursor were characterized at nanoscale by conductive atomic force microscopy (CAFM). For both films, the leakage current flows mainly through elevated grains and not along grain boundaries. The overall CAFM leakage current is larger and more localized for the TiCl₄-based films (0.63 nm capacitance equivalent oxide thickness, CET) compared to the Ti­(O-i-C₃H₇)₄-based films (0.68 nm CET). Both films have a physical thickness of ∼20 nm. The nanoscale leakage currents are consistent with macroscopic leakage currents from capacitor structures and are correlated with grain characteristics observed by topography maps and transmission electron microscopy as well as with X-ray diffraction