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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 mm2 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. [ABSTRACT FROM AUTHOR]

Thin-film Si-integrated inductors with closed cores have different magnetic field distributions in the winding window space compared to the inductors with unclosed cores. One-dimensional methods are no longer applicable for these inductors to calculate the ac resistance. Based on the analysis of the magnetic field distribution of the devices, a 2-D field solution was developed, which leads to an improved 2-D method to calculate the ac resistance of the device. High accuracy of this new approach has been verified by finite-element analysis, while 1-D methods can lead to significant errors. [ABSTRACT FROM AUTHOR]