High Frequency Characteristics Regulation Of Nickel-iron Thin Film And Its Application In Thin Film Inductors

Fabricating magnetic thin films with high saturation magnetization,high stability,low coercivity,and suitable resonance frequency is a key challenge in the development of high-frequency,integrated,miniaturized magnetic devices.This dissertation focuses on the research of nickel iron thin film materials and their applications in thin film inductors for on-chip systems.In terms of materials,the soft magnetic properties of Ni₈₁Fe₁₉（Py）thin films were optimized via double-sided pinning using materials with high saturation magnetization（i.e.Fe）.Furthermore,the magnetic anisotropy of these films was significantly modulated through various of control methods.This research systematically investigates the magnetization reversal process and high-frequency properties of the thin films.In terms of devices,based on the prepared high-frequency thin films,high-frequency,integrated,miniaturized thin-film inductors were designed,and a complete chain of research work regarding“magnetic thin film-process parameter-performance control-magnetic device application”was established.First,Py thin films with varying thicknesses were deposited on Si（100）substrates via electron beam deposition.Further,employing atomic force microscopy,vibrating sample magnetometer,and a vector network analyzer,the relationship between the microstructure,static magnetic properties,and high-frequency properties of the films with the thickness was established.In addition,a semi-quantitative analysis of the surface oxide layer of the films was conducted by angle-resolved X-ray photoelectron spectroscopy.The results indicate that changing the thickness of the Py thin films can effectively modulate their growth mode;the coercivity,surface roughness,and average grain size exhibit a nonmonotonic dependence on thickness,indicating excellent magnetostatic properties at a thickness of 100 nm.The thicknesses of Ni O,Ni（OH）₂,Fe₂O₃,and Fe O on the films were 0.21,0.3,0.9,and 0.71 nm,respectively.These findings provide support and important reference for future investigations on ultrathin multilayer films.Furthermore,the study explored the effects of vraying the high saturation magnetization Fe film,oblique angle,strain,and cycle number on the magnetic anisotropy and high-frequency performance of Ti/Fe/Py/Fe/Ti multilayer films.A systematic relationship between“magnetic thin film-process parameters-performance control”has been established,providing a foundational for future development of high-frequency,integrated,miniaturized thin-film inductors.The research yielded the following findings:（1）Altering the thickness of the Fe layer in the Ti/Fe/Py/Fe/Ti multilayer films effectively modulates the saturation magnetization and resonance frequency of the thin film.A clear correlation between the static magnetic properties and the varying thicknesses of the Fe film was established.（2）Oblique deposition of the Ti/Fe/Py/Fe/Ti multilayer films resulted in significant modulation of the magnetic anisotropy and high-frequency characteristics of multilayer film has been achieved.The magnetic anisotropy of the multilayer films was found to be monotonically dependent on the oblique angle.At increased oblique angles,the maximum uniaxial anisotropy field reached 495 Oe,and the corresponding resonance frequency was 4.71 GHz,approximately 3.6 times that of a normally deposited film on the same substrate.This relationship was linked to shape anisotropy caused by microscopic columnar morphology.（3）Employing a specialized sample holder allowed the Ti/Fe/Py/Fe/Ti multilayer films to be deposited on flexible polyethylene terephthalate（PET）substrates,introducing adjustable stress.This technique significantly regulated of the magnetic anisotropy of the multilayer films on PET substrates,establishing the relationship between magnetic anisotropy,magnetization flipping,and high-frequency characteristics.Increasing strain enhanced the remanence ratio of the easy-magnetization direction of the films and decreased that of the hard-magnetization direction,thus improving the high-frequency performance of the film by enhancing the uniaxial magnetic anisotropy field.Accordingly,the relationship between microstructure,magnetostatic properties,and strain was revealed.（4）Modifying the layer periodicity of Ti/[Fe/Py/Fe/Ti]_n multilayer films enabled the control of the microstructure,static magnetic properties,magnetic moment reversal,and high-frequency magnetic properties of the films.A cycle number dependent bimodal phenomenon of the first-order reversal curve distribution and magnetic spectrum was observed.Attributed to exchange interactions between adjacent magnetic domains.This modulation enabled tunin of the resonance frequency of the films from 1.27 to 2.44 GHz.Finally,based on the optimized multilayer films,the research and development of thin-film inductors were conducted,establishing the relationship between“magnetic thin film-magnetic device application”.The design parameters for thin-film inductors were optimized using the commercial software HFSS.The inductors were fabricated using the optimized MEMS technology,with thier electrical properties assessed using a probe stage.The results demonstrate that the inductance value and quality factor of the thin-film inductor based on the thin films were 172.9 n H and 17.6,respectively,at 100MHz.The comprehensive performances of the magnetic core inductors were significantly better than those of air-core inductors.