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Study on the Process and the Electromagnetic Properties of Fecob-based Nano-magnetic Thin Films

Author: LiaoJianSheng
Tutor: FengZeKun
School: Huazhong University of Science and Technology
Course: Microelectronics and Solid State Electronics
Keywords: Nano-Magnetic Thin Films FeCoB Permeability Anisotropy Fields
CLC: TN04
Type: Master's thesis
Year: 2009
Downloads: 45
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Abstract

Modern development of inductive devices requires high performance magnetic thin films for higher operation frequency and smaller size. In this article, we present the resent development of FeCo-based thin films, and then we simulate the complex permeability of the magnetic thin films based on the Landau-Lifschitz equation. In addition, we summarize the different kinds of anisotropy fields such as macroscopic shape anisotropy, random anisotropy, field induced anisotropy, magnetoelastic anisotropy, oblique-incident anisotropy as well as the anisotropy related with the film surface topology. The main losses principles are presented next, including the hysteresis loss, the eddy current loss as well as the loss resulted from the permeability resonance. Then we describe the main principles of magnetron sputtering and the typical process of preparing the magnetic films. Moreover, we present the typical problems met in common experimental procedures, and the detailed solutions are given respectively. These problems include the calibration of the vacuum meter, failure of plasma discharge resulted from the short-circuit in the target and the shielding metal, low sputtering rate due to the thickness of the target, fixation of the nonmagnetic chips on the target, choices of the substrate for better properties and the use of polymer substrate for composition analysis. In addition, we describe the corresponding analysis technique for the measurement of the films.We fully discuss the properties of the FeCoB films without adding an induced magnetic field in sputtering or post annealing procedure. The damping in the films is related with the film thickness. It is found that the thinnest film has the lowest damping in the film. Moreover, we find that the argon pressure has great effects on the film stress so as to affect the film properties. To attain better high frequency properties, it is essential to maintain the argon pressure at low levels. Then, we investigate the properties of the FeCoB-based films by changing the compositions and other procedures. In order to adjust the anisotropy field and the permeability in the film, we introduce the induced magnetic field during sputtering. To obtain higher resonance frequency and better soft properties, Ni is added to the film. To enhance the resistivity of the films, insulator SiO2 is appended. At last, we survey the effects of annealing. Due to the great effects of Ni, we investigate the content of Ni to the improvement of the film properties. It is essential to maintain Ni in appropriate low value to obtain good properties. Finally, excellent film properties are obtained: resonance frequency exceeds 2.2 GHz; the real and the imaginary part of permeability at 0.5 GHz are 476 and 92, respectively; the resistivity of the film reaches 682μ?·cm. In the last part of the article, based on the worldwide research works already done to date, we propose several possible ways to further improve the film properties.

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