[...]... frequency (RF) MEMS The term RF MEMS refers to the design and fabrication of MEMS for RF integrated circuits It should not be interpreted as the traditional MEMS devices operating at RF frequencies MEMS devices in RF MEMS are used for actuation or adjustment of a separate RF device or component, such as variable capacitors, switches, and filters Traditional MEMS can be divided into two classes: MEMS actuators... (1998), the RF MEMS development to date can be classified into the following categories based on whether one takes an RF or MEMS view point: (1) RF extrinsic in which the MEMS structure is located outside the RF circuit and actuates or controls other devices in the RF circuit In this class, one would consider the example of a tunable microstrip transmission line and associated 2 MEMS AND RF MEMS phased... structural materials were expected for MEMS, Figure 1.6 Freeform three-dimensional microfabrication (additive) 16 MEMS AND RF MEMS and much progress has been made (Cohen et al., 1999; Ikuta and Hirowatari, 1993; Jiang, Sun and Zhang, 1999; Takagi and Nakajima, 1993; Taylor et al., 1994; Zhang, Jiang and Sun, 1999) On the other hand, most sensing and actuating structures used in MEMS are fabricated from thin... antenna, but also increases the bandwidth Many MEMS based microwave components are aimed at reducing insertion loss and increasing bandwidth This third aspect is valid for surface micromachined devices such as RF switches, tunable capacitors and micro inductors Conventional RF switching systems such as PIN diodes tend to be inefficient at higher frequencies MEMS based RF switches with very low actuation... MEMS phased shifters and arrays Microstrip lines are extensively used to interconnect high-speed circuits and components because they can be fabricated by easy automated techniques (2) RF intrinsic in which the MEMS structure is located inside the RF circuit and has both the actuation and RF- circuit function In this class, one could consider traditional cantilever and diaphragm type MEMS which can be... years, and we are increasingly leaning towards their applications in microwave and millimeter wave systems, and even in optical systems Apart from having the advantages of bulk production, and being miniaturized, these can often lead to more efficient systems compared with conventional ones The need for micromachining and MEMS based systems for RF and microwave applications arise from the inherent limitations... micromachining is 6 MEMS AND RF MEMS Concave corner Isotropic wet etching: agitation Convex corner SiO2 mask Isotropic wet etching: no agitation Top view Cantilever beam (a) Anisotropic wet etching: (100) surface (100) Surface orientation Masking film (111) Buried etchstop layer (100) Surface orientation (111) 54.74˚ Silicon Side view Silicon (c) (100) Surface orientation Anisotropic wet etching: (110) surface Dielectric... book and are greatly appreciated In particular we also wish to thank many of our colleagues and students, Taeksoo Ji, Yanan Sha, Roopa Tellakula, Hargsoon Yoon, and Bei Zhu, at the Center for Electronic and Acoustic Materials and Devices for their contributions in preparing the manuscript for this book We would like to thank Professors Vasundara V Varadan and Richard McNitt for their support and encouragement... moulding) 4 MEMS AND RF MEMS and ‘glue mechanism’ using the photoforming process to fabricate complicated structures by combining components, each of them made by its best fabrication process Batch processing of such hybrid silicon and polymer devices thus seems feasible The combined architecture may also result in sheets of smart skin with integrated sensors and actuators at the µm to mm scale For some applications. .. microelectromechanical systems (MEMS) in many current and future radio frequency (RF) , microwave and millimeter wave systems Such devices are termed RF MEMS, although it encompasses all miniaturized devices; whether they are operated micromechanically, or fabricated by micromachining, or both Fortunately enough, the processing techniques for MEMS systems have improved significantly over the years, and we are increasingly .