Combining Ta[sub 2]O[sub 5] and Nb[sub 2]O[sub 5] in Bilayered Structures and Solid Solutions for Use in MIM Capacitors

Binary systems of and are investigated as dielectric materials that allow low-temperature fabrication and are suitable for use in metal-insulator-metal (MIM) capacitors. This investigation shows that a film is crystallized in a hexagonal symmetry at a temperature of less than 500°C, which is more than 250°C lower than the corresponding temperature for a film. Using as a nucleation layer lowers the crystallization temperature for to less than 500°C. This is because hexagonal is stably formed on the hexagonal by heteroepitaxy. A bilayer with a high dielectric constant of 50 can therefore be prepared by a 500°C fabrication process. Solid solutions of and are also investigated. The substitution of 10% in to form was found to decrease the temperature of crystallization from 700°C for pure to 550°C. The dielectric constant of the film is approximately 20% greater than that of the film. This is because the substitutional stabilizes the material in the hexagonal phase, which corresponds to a high dielectric constant, at lower temperatures.