Fabrication of CoFeB–SiO2 Films With Large Uniaxial Anisotropy by Facing Target Sputtering and its Application to High-Frequency Planar-Type Spiral Inductors

A comprehensive study on fabrication of CoFeB–SiO2 films with large in-plane magnetic anisotropy for the use in high-frequency inductors in power electronics circuits was conducted. The magnetic films were deposited using facing target sputtering (FTS), which can introduce large uniaxial magnetic anisotropy in the plane. A multilayer structure consisting of CoFeB–SiO2 and SiO2 layers suppressed columnar growth and thus reduced undesired perpendicular magnetic anisotropy (PMA). As a result, a <inline-formula> <tex-math notation="LaTeX">$1 ~\mu \text{m}$ </tex-math></inline-formula>-thick magnetic layer was achieved with excellent soft-magnetic properties and no stripe domain structure. The effectiveness of these magnetic films was demonstrated by fabricating and characterizing planar-type spiral coils. This development of micromagnetic inductors using the magnetic layer shows great potential for use in high-frequency power electronics applications.