| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 99 === Effects of the Hf content in Co-Hf-Ta thin films on the microstructure and magnetic properties were investigated in this study. Appropriate Hf addition can effectively refine the Co grain size, leading to the reduced magneto-crystalline anisotropy. The film with optimal Hf concentration of 2.81 at.% exhibits excellent soft magnetic properties: high saturation magnetization (4πMS ~ 13.6 kG), and low coercivity (HC ~ 0.6 Oe). The effective permeability of the film reaches 800 and remains constant up to 1 GHz.
A planar inductor integrated with Co-Hf-Ta ferromagnetic films was fabricated. The as-deposited Co-Hf-Ta film on the Al2O3 substrate with a thickness of 3 μm exhibits large saturation magnetization (4πMS) of 13.4 kG, and low coercivity (HC) of 0.4 Oe. The integrated inductor has current-carrying capability of more than 3 A and the inductance (2.23 µH) 25 % more than the air-core inductor (1.78 µH) at 5 MHz. In addition, there is a trade-off between the inductance enhancement and the saturation current or the high-frequency performance.
In addition, Co-Hf-Ta and Fe-Hf-O thin films are chosen to replace the top-drum for the commercial inductor. According to the simulation results, the Co-Hf-Ta thin film with high permeability of 800 effectively enhances the inductance up to 122 % at minor currents, while the 5µm thick Fe-Hf-O film with high HK of 100 Oe has capability for eliminating dramatic variations in the inductance at major imposed currents.
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