| The development of electronic devices operating at microwave frequency and device miniaturization has gone through more than several decades.Fe-N based magnetic films have been researched in electronic devices widely because of their high permeability and tunable resistivity at the high frequency.In this paper,the state of the art of Fe-N based films and related devices were introduced and discussed.At the same time,the magnetic properties of Fe N-based films and planar inductors at microwave frequency had also been explored by designing Fe N-Fe NHf multilayered film structures.It was found that the magnetic properties of the multilayered films were improved resulting from the low anisotropic field with the change of the bottom films.Remarkablely,the eddy current loss at high frequency of the multilayered films was also reduced by increasing the resistivity and improving the components of films.Moreover,the planar spiral inductors were fabricated by using Fe N-Fe NHf multilayered films instead of Fe N and Fe NHf single-layered films.The Fe N-Fe NHf multilayered films were applied to the preparation of planar spiral inductors.The effects of anisotropic fields with different bottom films on high-frequency inductors were also studied systematically.The detailed research contents of this paper were as follows:1.Different Fe N,Fe NHf single-layered soft magnetic films and Fe N-Fe NHf multilayered soft magnetic films were prepared by the high vacuum RF magnetron sputtering.The surface structure and properties of the films were characterized by SEM,VSM,vector network analyzer and other instruments.The properties of soft magnetic films were seriously affected by the film thickness and film element composition.By adding non-magnetic element Hf,the resistivity and permeability of Fe-N based single-layered soft magnetic films were improved.Using multilayered soft magnetic film structure can further improve the magnetic and electrical properties of the films.Experimental results indicated that permeability of the multilayered Fe N/Fe NHf films exhibited 612,showing an increase of 51%,compared to that of Fe NHf single-layered film above the frequency of0.5 GHz.Furthermore,Fe N/Fe NHf multilayered films were applied to the preparation of inductors,and the inductance was successfully increased by 19%.2.Landau-Lifshitz-Gilbert equation was used to fit the experimantal permeability versus frequency curves,then,the parameters of anisotropic field H_k,spin magnetic ratioγ、damping coefficientαcould be obtained.Herzer model was used to explain the 30%reduction of anisotropic field in multilayered films compared with single-layered films.At the same time,the impedance matching of the prepared inductance circuit was simulated by using advanced design system.The inductance value and quality factor Q value of the inductors were obtained by using the equivalent circuit method.3.Experimental results were combined with the theoretical calculations to verify the rationality of the experimental data.Eddy current loss mechanism was used to discuss the loss mechanism of inductors which theoretical value was slightly higher than the experimental value by 2%.The properties of multilayered films were also compared to those of single-layered films.The resonance frequency f_r and permeabilityμwith the changed properties of the bottom film were analyzed by Hoffmann theory.The performances of planar spiral inductors based on the Fe N-Fe NHf multilayered films were comprehensively analyzed in combination with the high frequency properties of magnetic films.The experimental and theoretical results indicated that the improvement of magnetic properties in Fe N-Fe NHf multilayered films,such as permeability and resonance frequency,stemed from the low anisotropic field.In present paper,the study of high frequency planar inductors based on the multilayered soft magnetic thin films and the performance of high frequency characteristics provided the experience of circuit design and performance of characterization for the application of soft magnetic thin films to microwave devices. |
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