Abstract
Soft magnetic thin films integrated to magnetic component, i.e. inductor, are considered as a potential solution to meet increasing demand for smaller dimension and light weight power conversion devices in portable electron products. In this study, the influences of oxygen flow rate on magnetic and high frequency properties of as-deposited Fe-Hf-O thin films were analyzed. These films exhibited mixed phases of α-Fe nanograins and amorphous HfO2 phase, showing nanocrystalline structure and soft magnetic properties. The Fe58.8Hf13.1O28.1 film with the optimum O2 flow rate of 1.2 sccm showed high saturation magnetization of 10.6 kG, high resistivity of 254 μΩ-cm, and flat μ' characteristics of 250 up to 1 GHz. The thickness effects on the characterization of Fe-Hf-O film with the O2 flow rate of 1.2 sccm were also investigated. The composition, resistivity, and saturation magnetization nearly maintained constant with varying thickness. As the film thickness increased from 0.5 to 5.5 μm, the coercivity (HC) decreased to a minimum value of 0.5 Oe and complex permeability gradually declined from nearly 300 to 160. In addition, a novel structure was proposed to incorporate commercially available inductor with as-fabricated Fe-Hf-O films of 0.5, 1.1, 3.3, and 5.5 μm. The inductance of integrated inductors increased from 3 % to 25 % with Fe-Hf-O film. The DC current characteristic of integrated inductor was improved by a thicker film. The performance of integrated inductors with 5.5-μm FeHfO and various coil turns of 7, 9, 11, and 15 was discussed. The integrated inductor with coil turns of 11 and 5.5 μm thick Fe-Hf-O film displayed high inductance of 1.34 μH and superimposed current of 1.76 A, exhibiting potential applications in DC/DC converter.