Design and fabrication of RF devices by novel MEMS technologies

Abstract

With today's fast expansion of the wireless communication industry, integrated circuits are being driven to a higher level of integration by consumer market that is desired for products with higher performance, low cost, light weight, small size, and minimum power dissipation. The active components such as, diodes, transistors, have been well developed for RFlCs (radio frequency integrated circuits) in the few GHz frequency range and they are easily integrated onto chips using today's IC technologies (CMOS, BiCOMS, BiPolar). However, for the development of RFlCs, passive components including inductors, capacitors, resistors, and filters et al. are indispensable. Unfortunately, these passive devices, especially inductors and filters, are still not satisfied with the RFlCs requirement. The bottlenecks for the full integration to realize SOC (system on chip) are the development of passive components such as inductors and filters with high quality factor and small size. Inductors are essential in RF circuits for functions such as tuning, filtering, impedance matching, and gain control. Nowadays, on-chip RF inductors are mostly fabricated on the GaAs substrate, which is much more expensive than silicon substrate and can not be integrated with silicon substrate. The fabrication of inductors on silicon substrate, like the other components based on silicon, can obviate the present need for external connections, thus resolving issues such as electrical and magnetic coupling as well as parasitic losses due to pad and bond wire in the RF designs. On the other hand, the commonly used silicon substrate has high conductivity in the high operating frequency range of up to few GHz. The i ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library My study years at NTU have exposed me to various challenging, invigorating and great experiences. I would like to take this opportunity to thank all the wonderful teachers, staffs, technicians and friends whom I have been fortunate to interact with during my lifetime. Firstly, I thank Professor Miao Jianmin, my Ph.D supervisor, for selflessly sharing his passion and love in Micro-Electro-Mechanical-System (MEMS) technologies and constantly giving guidance and helpful discussions. I am grateful to him for giving me the flexibility to work on anything that fit within the framework of this work and the encouragement to work on developments of RF devices. Special thanks would also be given to Professor Ma Jianguo and Ph.D student Ma Kaixue for the pleased cooperation in the research project of RF filters. Without their enthusiasm and knowledge, I would not have continued on for Ph.D study. I thank them for years of advice and friendship. I also thank the academic staffs involving Dr. Zhu Hong, Dr. Sun Tietun, Dr. Ciprian Iliescu, and Dr. Chen Longqing for the years of help rendered during my project experiment. I feel grateful to them in MMC, NTU for creating a healthy and dynamic environment for conducing research.