Tunable Low-Field Interdigitated Barium Strontium Titanate Capacitors

The rapid growth of communication systems demand for wide tunable low loss microwave components. Barium strontium titanate (BST) voltage dependent permittivity has shown a great potential impact for the fabrication of frequency agile components. In this work, BST interdigital capacitor (IDC) on silicon substrate exhibiting high tunability at low bias voltages is presented. The interdigital capacitor with a 3 μm gap is characterized. The tunability of 3:1 is obtained at bias voltage of 5 V. This corresponds to a 3.5 μm electrode gap width and a 5 V dc bias. Microwave measurements reveal a zero bias film quality of 50 around 30 GHz.