Through-Silicon via Coupled Inductors for Vertical Power Delivery

This article presents the design, fabrication, and characterization of through-silicon via (TSV) coupled inductors for vertical power delivery. The inductors are implemented by electrodepositing thin-film magnetic material onto via sidewalls and forming two coaxial Cu layers inside vias as coupled windings. The unique coaxial winding arrangement eases fabrication constraints. Many coupled inductors can be interconnected in a fabric-like fashion and scaled to larger inductance values and current ratings. As a proof of concept, TSV coupled inductors are fabricated, achieving an inductance density of 162 nH/mm2, an L/RDC ratio of 597 nH/Ω, a coupling factor of 0.97, and a peak Q of 9 at 5.5 MHz. Inductor performance with different core thicknesses and via diameters is evaluated, showing the potential to exceed 1000 nH/mm2 in inductance density and 2500 nH/Ω in L/RDC ratio.