A Novel Thin Film Cascade Matrix Coupled Inductor for Integrated Voltage Regulators

Abstract

This letter demonstrates an on-silicon integrated thin film coupled inductor using a novel cascade matrix concept to suit multiphase integrated voltage regulator (IVR) applications. The novel cascade matrix coupled (CMC) stripline inductor facilitates all-phase-coupled configuration to reduce the phase ripple current in IVRs. It also shows excellent scalability and neat floor planning. Moreover, the proposed CMC inductor uses double layer metal scheme for windings and interconnects, which significantly reduces the ac winding resistance. A four-phase CMC inductor has been successfully fabricated on-silicon substrate and characterized, which uses conventional thin film magnetic core deposition process to achieve in-plane magnetic uniaxial anisotropy. The device occupies 3.2 × 1.7 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> floor area and provides 19.5 nH phase inductance with 120 mΩ dc resistance. The saturation current for each phase is up to 0.4 A when the phase inductance drops by approximately 20%. The coupling coefficient between any two phases of the proposed CMC inductor is 0.27, much higher and more controllable than that of toroid core-based coupled inductors.