A MEMS Spiral Power Inductor with A Magnetic Core for DC-DC Converters

This paper reports a novel wafer-level fabrication process of a spiral power inductor for DC-DC converters. The inductor features 250 μm-thick copper windings to meet the needs of power devices. The inductor is fabricated with the silicon substrate removed for high Q and wrapped with magnetic materials to achieve high inductance. By using an electroless nickel immersion gold plating process, the inductor terminals are seamlessly connected with copper core solder balls, facilitating the convenience of flip-chip assembly. With a form factor of only 2.5 × 2.5 × 0.65 mm
³
, the fabricated power inductor achieves a measured inductance of 200 nH at 1 MHz and a Q factor of 17.8 at 81 MHz.