Magnetic properties of (Ni0.81Fe0.19/SiO2)n multilayers for high frequency on-wafer inductor applications

Abstract

We investigated the magnetic properties of multilayer stacks of Ni81Fe19 thin films separated with SiO2 intended for use in inductors operating at sub-GHz frequencies. We measured saturation magnetization, anisotropy field, coercivity, and complex permeability of sputtered multilayer structures consisting of thin film stacks of 5, 10, 15, 20, and 25 layers, ranging from 160 to 1455 nm in total magnetic material thickness. Our analysis indicates that multilayer stacks composed of repeated layers thinner than 115 nm generally maintained the desired magnetic properties found in individual thin films, such as high permeability, low anisotropy, and low coercive field. Moreover, the multilayer stacks did not exhibit unwanted characteristics such as stripe domain formation and decreased value of real permeability, which commonly occurred in single thicker films. These properties make them suitable for on-wafer inductor applications.