| Miniaturization and multi-function are the development trends of modern electronic devices,and micro-inductor is one of the most basic electronic components.Accordingly,chip inductor integration technology has become an important hotspot in industry.Therefore,the structure,composition and manufacturing process of the magnetic core inductor have been extensively studied,focusing on the development of novel magnetic core film material.Fe-Ni alloys have received a great attention as a consequence of its high saturation magnetization(Bs),low magnetostriction(Bs),small coercive force(Hc)as well as low thermal expansion coefficient.Due to these excellent soft magnetic properties,Fe-Ni alloys have been used widely in a variety of micro-fabrication techniques and industrial application.Compared with other preparation techniques including sputtering and screen printing,electrodeposition is the most versatile method in microelectromechanical systems(MEMS)due to its flexibility,quality,capability and low cost.What’s more,in order to prevent any heat treatment from damaging electronic components,electroplating is a good candidate for the fabrication of soft magnetic thin film at low temperature.Considering these superiorities of electrodeposition,it is possible to provide a variety of soft magnetic thin films on complex geometries by tuning the deposition conditions.As a controllable method,magnetic field which exchanges coupling with electric field was applied during the electrochemistry process to improve the magnetic properties of iron-nickel alloy in this study.Firstly,binary Fe-Ni thin films were fabricated on wafer by applying 100mT external magnetic field during electroplating,and the function of in-plane parallel magnetic field in the course of the plating experiment and magnetic properties have been studied.Magnetic measurements show that in-plane anisotropy field can be obtained by magnet-electroplating,and the magnetic properties are very sensitive to the thickness of film.The Ni70Fe30 film with thickness of both 0.6μm and 1.2μm exhibit significantly uniaxial surface anisotropy and the complex permeability of the direction of parallel magnetic field can reach about 220,while 2μm Fe-Ni thin film does not have a uniaxial magnetic anisotropy.The deposition rate of the coating under the magnetic field is up to 0.36 μm/min,and the fabricated film has properties of Bs 1.5T and He 1.40e.In order to enhance the resistance and decrease the coercivity of the binary Fe-Ni film,the P and RE elements are introduced to electrodeposit Fe-Ni-P(RE)alloy.After the application of the magnetic field,the crystal grains are refined,and the number of pores generated on the surface is remarkably reduced.The introduction of external magnetic field can significantly improve the deposition rate and dynamic permeability.And the ferromagnetic-resonance(fFMR)frequency can achieve 500MHz under 40mT magnetic field.Specifically,the in-plane anisotropy of the film deposited at a magnetic field of 10mT was calculated to be approximately 1160e using the area integral method,which is obviously higher than that of the binary Fe-Ni material.It is concluded that the in-plane anisotropy of Fe-Ni based films can be successfully induced by introducing an external magnetic field in the electrodeposition process.The application of the magnetic field during deposition can also significantly improve the soft magnetic properties of the film as well as the cut-off frequency,which make Fe-Ni based material a good candidate as a high performance magnetic core. |
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