Coupled Inductors With Crossed Anisotropy CoZrTa/SiO₂ Multilayer Cores

Four-turn coupled (flux-closed) inductor structures have been fabricated and tested for use in high-power-density integrated voltage regulator (IVR) applications. Our solenoid-like structure is comprised of a laminated magnetic core of four rungs surrounded by four Cu windings creating four coupled inductors. The magnetic core is made of laminations of ultra-high-vacuum-sputtered [5 nm Ta/200 nm Co91.5Zr4.0Ta4.5(CZT)/7 nm SiO2] repeated 20 times. Individual CZT layers are deposited under a magnetic bias to induce uniaxial anisotropy. The quad-coupled inductor shows a frequency response with a measured self-inductance of 7.4 nH for one inductor sustained up to 100 MHz and roll-off to half this low-frequency value at ~450 MHz. This inductance is more than 65× higher than what would be calculated from an air-core inductor of equivalent geometry.