Micro-fabricated thin-film inductors for on-chip power conversion

This paper reports an optimized design and micro-fabrication approach for silicon-integrated elongated-spiral inductors for on-chip power conversion. The inductors are designed for high-power-density and high-efficiency DC-DC converters which transfer 25 W of power at frequencies between 5 and 30 MHz. The predicted power density of the inductors is close to 1 W/mm(exp 2) with predicted overall converter efficiencies exceeding 90%. A Co-Zr-O multilayer thin-film magnetic material surrounds the planar copper windings of the inductor within etched silicon trenches. Materials and most processing steps have been experimentally verified. The miniaturization and integration of high-efficiency inductors on silicon can enable radical reductions in the size and cost of power converters for a myriad of applications.