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

使用块状铁氧体材料会干扰磁性设备和移动通信设备的实现。本研究的目的是开发低温铁氧体薄膜的制备技术，并探讨其在小型、低高度磁性器件中的应用可行性。研究结果如下：1。利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矫顽力低至11 Oe、高取向的Ni-Zn铁氧体薄膜。采用锥形溅射靶代替血小板靶是实现这一目标的有效方法。研制了以镍锌铁氧体薄膜为材料的极小尺寸电感器。在1 GHz范围内，电感比无磁芯电感增大25%，q值比无磁芯电感增大15%。该电感器的面积为6×10^4μm^2 (250μm×240μm)，约为其他研究人员已经开发的最小电感器的50%。从而证明了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结构新颖的铁氧体薄膜微带Y结型隔离器。该隔离器的高度小于1mm。Y型结圆形部分的下接地面靠近微带线，以增强微波传输的循环。采用微加工技术对隔振器进行了试制。隔离器具有非互反传输特性

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