Development of Fabrication Technology of Ferrite Thin Materials for Microwave Magnetic Devices

块状铁氧体材料的使用妨碍了磁性器件和移动的通信装置的实现。本研究旨在发展低温下铁氧体薄膜的制造技术，并探讨其应用于小型低高度磁性元件的可行性。取得了以下研究成果1。采用电子回旋共振微波等离子体反应溅射技术，以44 nm/min的高沉积速率成功制备了具有低至11 Oe的结晶度和高取向度的Ni-Zn铁氧体薄膜。研制了镍锌铁氧体薄膜超小型电感器。与无磁芯电感器相比，在1GHz以下获得电感增加25%和Q值增加15%。该电感器的面积为6× 104 μ m2（250μm×240μm），约为另一位研究人员已经开发出的最小电感器的50%。因此，证明了使用铁氧体薄膜作为磁芯的有效性。利用高频有限元仿真器设计了一种新型结构的铁氧体薄膜微带Y结型隔离器。该隔离器的高度小于1 mm，接地面位于Y结圆形部分下方靠近微带线的位置，以增强微波传输的循环性。采用微机械加工技术试制了隔离器。该隔离器具有非互易传输特性

Use of bulk ferrite materials disturbs achievement of magnetic devices and mobile communication sets. The purpose of this research is to develop fabrication technology of ferrite thin-films at low temperature and to investigate the feasibility of application to small and low height magnetic devices. The following research results were obtained1. Using reactive sputtering utilizing electron-cyclotron-resonance microwave plasma, Ni-Zn ferrite thin-films with a coercivity as low as 11 Oe and high crystal orientation was successfully prepared at high deposition rate of 44 nm/min. Use of conic sputtering target instead of platelet target was effective to achieve this2. Extremely small size inductor using Ni-Zn ferrite thin-film was developed. 25 % increase in inductance and 15 % increase in Q-value as compared with inductor without magnetic core was obtained up to 1 GHz. The area of the inductor was 6×10^4μm^2 (250μm×240μm) which was about 50 % of the smallest inductor already developed by another researchers. Thus the effectiveness of use of ferrite thin-film as a magnetic core was proved3. Microstrip Y junction type isolator using ferrite thin-film with a novel structure was designed using high frequency FEM simulator. The height of this isolator was less than 1 mm. Ground plane underneath of the circle portion of the Y junction was located closed to the microstrip line to enhance circulation of microwave transmission. The isolator was fabricated in trial using micromachining technology. The isolator showed non-reciprocal transmission characteristics