Integrated (Ba,Sr) TiO3 (BST) films on copper and alumina for monolithic microwave integrated circuit (MMIC) applications

For development of tunable dielectric microwave devices, the ability to integrate ferroelectric and paraelectric films with low loss dielectric substrates, such as alumina, and with high conductivity metal top and bottom electrodes and vias, such as copper, is of interest. Reducing atmosphere processing has been developed to enable tunable dielectric monolithic microwave integrated circuit (MMIC) devices including tunable capacitors, phase shifters, distributed transmission line true time delay (TTD) elements, and combline filters on alumina substrates. Process and integration details of tunable BST circuit fabrication with novel copper-tungsten vias and semiconducting TaN biasing electrodes are presented.