High efficiency on-silicon coupled inductors using stacked copper windings

On-silicon coupled inductors with integrated magnetic material offer improved voltage regulator performance particularly in high power density applications such as microprocessor power delivery. The on-silicon coupled inductor designs reported in literature typically use single layer metal for winding deposition. In this paper we report on design, optimization and fabrication of two on-silicon coupled inductor designs with different coupling factors (0.4 & 0.8) using stacked copper coils or double layer metal for winding deposition. Initial frequency dependent electrical characterization of self-inductance confirms the predicted design values. Based on the large signal test data the predicted efficiency of both on-silicon coupled inductors is around 90 %.