Analysis of Integrated Solenoid Inductor With Closed Magnetic Core

The effect of a closed magnetic core structure on an integrated inductor was investigated by winding two series connected inductors around a stretched hexagonal ring of CoTaZr. The 8.5 and 17.5 turn inductors were fabricated using standard silicon process, and simulations were performed using Ansoft HFSS software. The resulting inductance of the device showed no improvement over two inductors without the closed magnetic cores, indicating that the closed core structure was insufficient to enhance the mutual inductance between the two devices. This was attributed to the uniaxial anisotropy of the magnetic film, which prevented the film from routing the generated flux circularly around the core. Therefore, while the physical shape of the magnetic film was closed, the effective magnetic shape maintained an air gap.