Integration of microwave phase shifter with BST varactor onto TiO2/Si wafer

A BST ferroelectric thin-film microwave phase shifter with interdigital capacitors on TiO₂/Si substrate is presented. The interdigital capacitors have 230 mum signal width, 100 mum signal to ground gap, and 10 mum finger gap. The device, with phase shifts of 142deg and FoM of 107.3deg/dB applied voltage of 50 V at 16 GHz, has been realised. The TiO₂ buffer layer grown by ALD enables successful integration of BST-based microwave tunable devices with Si wafer.