Functional graded high-K (Ba1-xSrx)TiO3 thin films for capacitor structures with low temperature coefficient

The high dielectric constant of perovskite-type alkaline earth titanates makes them attractive for use in integrated thin film capacitors for microwave circuits. The application temperatures of those devices such as resonators, filters and phase shifters range from cryogenic temperatures for superconducting devices up to 250 degrees C for semiconducting ICs. Significant material modifications have to be introduced to bring the pure components such as BaTiO3 and SrTiO3 into formulations which have a suitable temperature coefficient of the dielectric constant. For conventional powder based industrial processes, usually solid solution adaptations and heterogeneous mixtures are employed. The deposition processes of thin films, especially the low cost Chemical Solution Deposition (CSD) technique, offer the possibility to build thin films of graded compositions. We will show that in those films the composition gradient can be tailored in order to fit the designated temperature characteristics.