Electrodeposition of Titania Thin Films on Metallic Surface for High-k Dielectric Applications

Current microelectronics devices based on flexible as well as rigid substrates demand high dielectric constant (k) films to be grown on conductive substrate from a low-cost, low-temperature deposition technique. In this study, we produced high-k titania (TiO2) films through an affordable electrodeposition protocol from the electrochemical bath maintained at about 0 degrees C. The deposition occurs through a rapid hydrolysis mechanism of titanium containing ions in the precursor solution aided by electrochemically generated hydroxyl ions formed near the cathode surface (copper (Cu) substrate). Upon attaining a sufficient supersaturation level, such hydrolyzed species precipitate to form a titania thin film on the cathode surface. While depositing from a highly acidic precursor solution, Cu substrate was protected by a cathodic potential (-3 to -5 V against the counter electrode). The resultant titania films show nanoparticulate structures evolved from nucleation and growth events of the in situ precipitated particles. Much higher deposition rate (about 1 mu m/min) was observed compared with that of typical chemical bath deposition. The resultant films with a thickness of 1500 nm grown on Cu exhibit very high dielectric properties (e.g., k similar to 30, capacitance density > 110 nF/in.2 at 100 kHz) and moderate breakdown voltage (V-B) (similar to 17.5 V). These properties indicate the potential of electrodeposited titania films to be used as a small-area thin-film capacitor for miniaturized electronic devices.