射频/微波MEMS接触式开关的研究

【作者】 胡梅丽；

【导师】 赖宗声； 茅惠兵；

【作者基本信息】 华东师范大学 ， 微电子学与固体电子学， 2004， 硕士

【摘要】 目前无线通信中的射频／微波MEMS器件已成为国际上的研究热点，MEMS开关作为射频／微波通信中实现信号路由转换的重要器件，成为了研究焦点。与传统上的微波开关PIN管和GaAs FET相比，MEMS开关有尺寸小，插入损耗小，隔离度大，线性度好，工作频段范围大，直流功率小等优点。本文讨论的MEMS接触式开关是利用表面微机械加工技术制备出来的一种可以应用在0—5GHz频段的射频／微波开关。 本文在广泛文献调研的基础上，分析了接触式开关的工作原理，并用ANSYS7.0和HFSS8.0软件对器件进行了有限元动态加载模拟和微波参数的模拟，最终设计了以信号线中间断开的CPW为传输线、以SiO₂为桥墩、以铝硅合金和Au—Si₃N₄—Al复合材料为梁的空气桥接触式开关。并推导了这种两端固定，两个下电极结构的接触式开关的下拉电压的公式。以SiO₂为桥墩的空气桥结构在国内未见报道。 在多次改版、流片的基础上，围绕制备工艺中的一些关键技术，对器件版图和工艺作了改进和完善，设计了满足实验室工艺精度的器件版图，提出了适用于该器件的工艺流程。经过多次的流片，成功地制备出了MEMS开关的样品。制备研究中，采用厚胶（负胶）和聚酰亚胺作为牺牲层材料，对牺牲层的前烘、坚膜和刻蚀技术做了重点研究，取得了有特色的研究结果。 目前我们制备的两种MEMS开关样品，一种为下拉电压较低的铝硅合金梁MEMS开关，另一种为开关寿命较长的Au—Si₃N₄—Al复合梁MEMS开关。样品的测试结果都到达了隔离度30dB@5GHz，插入损耗小于2dB@5GHz的要求。此外，我们还对MEMS开关的商品化进行了研究。对制备出的MEMS开关的样品进行了封装和初步测试。 本文以射频／微波MEMS接触式开关这一重要的微波器件为研究对象，对该器件工作原理、模拟、设计、加工、测试到封装进行了较全面的研究。设计了一种适合接触式开关的空气桥式结构，并对开关制备中的重要工艺——牺牲层技术进行了研究。实验结果显示本文的MEMS开关的设计是合理的，工艺实现是可行的，实际器件特性与理论分析是一致的，说明了MEMS系统可应用于射频／微波通信领域，该技术具有巨大的发展潜力。更多还原

【Abstract】 At the present, microwave MEMS devices applied in the wireless communication is a focus of the research in the world. MEMS switch is a core device of microwave communications, that it can realize route-conversion. Compared with traditional microwave devices MEMS switch has some advantages, such as low insertion loss high isolatin, good linear characterN wide applied frequency range and low power. In this paper the switch that we researched is manufactured by surface micromachining process and is applied in 0-1 OGHz.On the basis of research, we analyzed the operating principles of MEMS contactswitch. And we apply the softwares--ANSYS and HFSS to simulate how theswitch works. The results of the simulation make us understand the devices more and make the optimization of the devices’ structure feasible. The switch includes SiO2 anchor CPW of disconnected single line and air-bridge structure. We base the results to design the switch’s layout and the process parameters of the switch.After lots of experiments, we improved on the device layout and fabrication process. And we put forward some new fabrication process and design the new device layout that satisfied the process condition of laboratory. MEMS switch samples are successfully made out. In the process, use negative photo resist and polyimide as sacrificial layer. The key processes for sacrifiaial layer technology are soft baking hard baking and etching. These are the focuses that we research.The test results indicate that isolation is higher 30dB at 10GHz and the insertion loss is lower than 2dB at 1 OGHz. In addition, we made the research for the product of MEMS switch and packaged the sample of the switch.In summary, based on MEMS technology, we research the MEMS switch of operations principles, simulations, design, fabrications, tests and package. We design new structure for serial switch. And emphasize on the sacrificial layer technology. The experiments results show that: the design is reasonable; the fabrication processes are feasible and the devices’ characteristics are in accordance with the principle analysis. These also show the feasibility of using the MEMS technology in microwave communication field and the potential of MEMS technology.更多还原