A Reconfigurable Inductor Based on Vanadium Dioxide Insulator-to-Metal Transition

This letter introduces a reconfigurable planar square-coil-shaped inductor exploiting as the tuning mechanism the insulator-to-metal transition (IMT) of a vanadium dioxide (VO2) switch placed in the interwinding space in an unprecedented manner. The VO2 thin-film bar-shaped switch is electrically connected to provide a temperature-selective current path that effectively short-circuits a part of the inductor coil changing the inductance of the device. The inductor is fabricated on a high-resistivity silicon substrate using a CMOS-compatible 2-D planar low-cost technology (four photolithography steps). The design, optimized to work in the 4-10-GHz range, provides measured inductances at 5 GHz of 2.1 nH at 20 degrees C and 1.35 nH at 100 degrees C with good stability in the entire frequency band (4-10 GHz) resulting in a reconfiguration ratio of 55%. The quality factor (Q-factor) at 7 GHz is about 8 at 20 degrees C (off state) and 3 at 100 degrees C (on state), outperforming tunable inductors employing VO2 with 2 orders of magnitude higher Q-factor and a smaller footprint. This represents an advancement for the state of the art of 2-D CMOS-compatible inductors in the considered frequency range.