Effects of the stacking levels on permeability characteristics and soft magnetic properties in FeCoHfAlO/AlOx multilayered films

In the communication industry, miniaturization is highly required for inductor devices. In order to miniature the dimension of inductors, high inductance is necessary. For this purpose, to employ high-permeability magnetic films enhances the inductance of inductors. For high-permeability, in-plane uniaxial anisotropy is a critical demand. The FeCoHfAlO/AlO_x multilayered films were fabricated by dc reactive magnetron sputtering. Due to the insertion of AlO_x layers, the out-of-plane uniaxial anisotropy of the FeCoHfAlO magnetic films is reduced and their resistivity is also raised. Therefore, the permeability of the FeCoHfAlO/AlO_x multilayers will be increased further. With the optimum configuration of a seven-layer structure [FeCoHfAlO (171 nm)/AlO_x (10 nm)]₇, high resistivity (ρ ~ 7490 μΩcm) and high-permeability (μ′ > 90 at 30-50 MHz) were obtained. The permeability increased nearly ten times from 9 (3 layers) to 98 (7 layers).