Characteristics of film type inductors using a FeZrBAg magnetic material

Two types of double rectangular spiral thin-film inductors with a multi-layer structure of magnetic film/conduction film/magnetic film were fabricated using a Fe_86.7Zr_3.3B₄Ag₆ thin film with high permeability and resistance, in which easy axis of magnetization of the thin-film was perpendicular or parallel to the current direction. The dependence of inductance and resonance frequency on the inductor type indicated that the perpendicular geometry inductor has higher inductance than the parallel geometry one, because spins of magnetic film align more easily along the field direction due to higher field intensity in the perpendicular geometry. However, the increase of the inductance, resulted in the decrease of resonance frequency. Then the effects of permeability of the magnetic film on inductance and resistance of the perpendicular geometry inductor were investigated. The permeability was controlled by annealing the film at different temperatures. With increasing the permeability, the inductance increased, but the resistance also increased due to the increase in magnetic core loss. As the resonance frequency was higher in air-core inductor than in magnetic thin-film core inductor, it is suggested to increase the resonance frequency which is characteristic of the air-core inductor rather than magnetic properties of the magnetic thin-film should be enhanced.