Design and fabrication of integrated power inductor based on silicon molding technology

This paper reports a new fabrication process that can be used to integrate high-power-density and low-loss inductors with silicon-based power ICs to realize monolithic integration of power converters for portable electronics applications. In this new process, copper is electroplated into through-wafer silicon trenches, resulting in thick copper windings (200-500 μm) and thus low winding resistance. The magnetic cores are electroplated on both sides of the silicon substrate to cover the copper windings, and through-wafer magnetic vias are used to close the magnetic path. Powder permalloy with relatively high resistivity (400 μΩω.cm) and low permeability (40) are used to reduce the loss of large magnetic cores. The powder permalloy can be fabricated by using high-current-density electroplating without mixing or high temperature sintering. A pot-core inductor has been designed and fabricated. The inductance and saturation current of the designed inductor are 179 nH and 5 A, respectively. The measured winding resistance of the 200 μm thick copper winding is 23 mω.