RF MEMS for high-frequency applications

IEEE Transactions on Microwave Theory and Techniques, 1998

This paper deals with a relatively new area of radio-frequency (RF) technology based on microelectromechanical systems (MEMS). RF MEMS provides a class of new devices and components which display superior high-frequency performance relative to conventional (usually semiconductor) devices, and which enable new system capabilities. In addition, MEMS devices are designed and fabricated by techniques similar to those of very large-scale integration, and can be manufactured by traditional batch-processing methods. In this paper, the only device addressed is the electrostatic microswitch-perhaps the paradigm RF-MEMS device. Through its superior performance characteristics, the microswitch is being developed in a number of existing circuits and systems, including radio front-ends, capacitor banks, and time-delay networks. The superior performance combined with ultra-low-power dissipation and large-scale integration should enable new system functionality as well. Two possibilities addressed here are quasi-optical beam steering and electrically reconfigurable antennas.

2003

RF MEMS have been pursued for more than a decade as a solution to high-performance on-chip fixed, tunable and switchable passives. However, the implementation of RF-MEMS into products has remained elusive. This is partly due to special-purpose processes that only supported a narrow application field, in many cases optimized for single devices. This prevented aggregation of volumes to justify the

RF MEMS are assuming a great importance in the fast evolving telecommunication market and space applications. In the last years a flexible technology platform has been developed and continuously optimized at FBK (Italy) for the fabrication of RF MEMS basic components as well as complex RF circuits working in the frequency range from sub-GHz up to more than 100 GHz. The paper reports about the fabrication process and its capabilities. The most important process features are described together with some modifications required for the manufacturing of specific devices, like dielectric less RF MEMS switches. Examples of produced devices and their performances are briefly presented.

RF MEMS technology can offer enhanced performance over the conventional solid-state devices. Along with other RF MEMS components, antennas have been investigated. This paper presents a unique review and survey of RF MEMS antennas. Here, antennas can be categorized into (i) generic antennas and (ii) antenna circuits. The former employs some forms of mechanical actuation for movements of the radiation elements. With the latter, individual radiation elements are physically stationary and integrated with RF MEMS switches and/or variable capacitors to alter their electrical length and diversity. In addition, (iii) antenna subsystems incorporating RF MEMS tuneable circuits and beam forming networks should not be overlooked. Examples of these antenna categories are described and conclusions drawn.

Journal of microelectromechanical systems, 2005

Design considerations and process development for fabricating radio frequency microelectromechanical systems (RF MEMS) switches on microwave laminate printed circuit boards (PCBs) are presented in details in this work. Two key processes, high-density inductively coupled plasma chemical vapor deposition (HDICP CVD) for low-temperature silicon nitride deposition, and compressive molding planarization (COMP) have been developed for fabricating RF MEMS switches on PCB. The effects of process conditions of HDICP CVD on low-temperature nitride film are fully characterized for its use in RF MEMS switches on PCB. Not only can COMP planarize the surface of the photoresist for lithographic patterning over topologically complex surfaces, but also simultaneously create a membrane relief pattern on the surface of a MEMS structure. Several membrane-type capacitive switches have been fabricated showing excellent RF performance and dynamic responses similar to those on semiconductor substrates. This technology promises the potential of enabling further monolithic integration of switches with other RF components, such as antennas, microwave monolithic integrated circuits (MMICs), phase shifters, tunable filters, and transmission lines on the same PCBs reducing the losses due to impedance mismatching from components/system assembly and simplifies the design of the whole RF system. [1416] Index Terms-Compressive molding planarization (COMP), high-density inductively coupled plasma chemical vapor deposition (HDICP CVD), printed circuit board (PCB), radio frequency microelectromechanical systems (RF MEMS) switches. I. INTRODUCTION R ECENT advancement in RF MEMS technologies have lead to superior switch characteristics, i.e., very low insertion loss, very low-power requirements, and high isolation to the conventional semiconductor devices [1]-[9]. Various RF subsystem circuits employing radio frequency microelectromechanical systems (RF MEMS) switches, such as variable capacitors, tunable filters, and phase shifters have been subsequently demonstrated on substrates such as silicon, GaAs, quartz, etc., showing much improved performance [10]-[12]. These successes have promised its potential to revolutionize

2009 Asia Pacific Microwave Conference, 2009

This paper presents a complete study from design to fabrication and characterization of a RF-MEMS switch implemented in Si-BCB technology. The topology of the switch is a cantilever which will be integrated into tunable filters for applications from W-frequency band to V-frequency band. Along the whole process, attention has been paid to correlate simulations (electromagnetic and mechanical) and technology parameters in order to ensure a reliable switch model. The measured RF performances of this component exhibit isolation around 15 dB at 60GHz in the up-state position and an insertion loss less than 2dB in the down-state.

2005

This work investigates the fabrication of a RF (ratio frequency) MEMS (micro elector mechanical system) switch using the standard 0.35 mm 2P4M (double polysilicon four metal) CMOS (complementary metal oxide semiconductor) process and the post-process. The switch is a capacitive type, which is actuated by an electrostatic force. The structure of the switch consists of a CPW (coplanar waveguides) transmission lines and a suspended membrane. The CPW lines and the membrane are the metal layers of the CMOS process. The main advantage of the RF switch is only needed a simple post-process, which is compatible with the CMOS process. The post-process uses an etchant, silox vapox III, to etch oxide layer to release the suspended membrane and springs. Experiment results show that the pull-in voltage of the switch is about 17 V. The insertion loss and return loss in the range of 10 to 40 GHz are-2.5 dB and-13 dB, respectively.

MEMS Sensors - Design and Application, 2018

Radio frequency microelectromechanical system (RF-MEMS) switches have demonstrated superior electrical performance (lower loss and higher isolation) compared to semiconductor-based devices to implement reconigurable microwave and millimeter (mm)-wave circuits. In this chapter, electrostatically actuated RF-MEMS switch conigurations that can be easily integrated in uniplanar circuits are presented. The design procedure and fabrication process of RF-MEMS switch topologies able to control the propagating modes of multimodal uniplanar structures (those based on a combination of coplanar waveguide (CPW), coplanar stripline (CPS), and slotline) will be described in detail. Generalized electrical (multimodal) and mechanical models will be presented and applied to the switch design and simulation. The switch-simulated results are compared to measurements, conirming the expected performances. Using an integrated RF-MEMS surface micromachining process, high-performance multimodal reconigurable circuits, such as phase switches and ilters, are developed with the proposed switch conigurations. The design and optimization of these circuits are discussed and the simulated results compared to measurements.

… Integrated Circuits in …, 2003

Key elements for switching matrices are reported. Single RF-MEMS toggle switches yield an insertion loss of 0.2 dB @ 30 GHz and an isolation of 25dB @ 30 GHz. Shielded RF crosses for routing the signal path in the switching matrix yield an insertion loss of 0.75dB @ 20 GHz in the under-cross path and 0.6 dB (simulated) in the over-cross path with an isolation higher than 40dB between under-and over-cross path. Double 90 degree bends with compensated air-bridges show an insertion loss of less than 0.1dB up to 20 GHz.

Sadhana, 2013

RF characterization and packaging of a single pole single throw (SPST) direct contact microelectromechanical (MEMS) series radio frequency (RF) switch is reported. Precise thickness of the silicon MEMS structure is achieved using a specially developed silicon Deep Reactive Ion Etching (DRIE) thinning process. A stress free release process is employed which ensures a high yield of released microstructures. The design of the device is based on stiffness equations derived from first principles. Displacement of the actuator under applied field is measured to confirm electrostatic pull in, which occurs in the 30-50 V range. The variation of contact resistance with time has been measured and is found to have a power law decay, in agreement with theoretical models. At the bare die level the insertion loss, return loss and the isolation of the switch were measured to be −0.43 dB, −25 dB and −21 dB, respectively at 10 GHz. The devices were packaged in commercially available RF packages and mounted in alumina boards for post package characterization. Due to the presence of bond wires in the signal path of the packaged devices, the RF performance was found to degrade at high frequencies. However, losses were measured to be at acceptable levels up to 2 GHz. Factors contributing to insertion loss at the die and package device levels are discussed in detail with possible solutions.