MEMS switch is a movable device manufactured by means of semiconductor technology, possessing many incomparable advantages such as a small volume, low power consumption, high integration, etc. This paper reviews recent research of MEMS switches, pointing out the important performance indexes and systematically summarizing the classification according to driving principles. Then, a comparative study of current MEMS switches stressing their strengths and drawbacks is presented, based on performance requirements such as driven voltage, power consumption, and reliability. The efforts of teams to optimize MEMS switches are introduced and the applications of switches with different driving principles are also briefly reviewed. Furthermore, the development trend of MEMS switch and the research gaps are discussed. Finally, a summary and forecast about MEMS switches is given with the aim of providing a reference for future research in this domain.

Research Status and Development Trend of MEMS Switches: A Review.

This paper is designed to review the MEMS switch by considering key aspects on the basis of mechanical structure, actuation methods, and types of contact and circuit configurations. The cantilevered and clamped–clamped switch structures are explored and discussed. Actuation methods and switch configurations have also been covered to give more insights about their placements and performances in RF systems. The electrostatic and piezoelectric actuation mechanisms can result in fast RF MEMS switches and better reliability but at the cost of increased pull-in voltage. The electrostatic method is mostly employed in MEMS switches due to its distinctive advantages. The resistive switch uses less actuation voltage compare to a capacitive switch but suffers from reliability issue. Nevertheless, the capacitive MEMS switches are prominent in use over ohmic contact switches due to better RF performance and reliabilities by offering lifetime of 3–10 million cycles. The RF MEMS switches can be placed in series, shunt and mixed configurations as per application requirements. Capacitive switches are mostly utilized in RF systems and placed in shunt with coplanar waveguide signal lines. These RF MEMS switches find applications in sensors, resonators, amplifiers, phase shifters, and MEMS satellite vehicles for space applications.

A review on RF micro-electro-mechanical-systems (MEMS) switch for radio frequency applications

A state of the art review on Radio Frequency Micro-Electromechanical Systems (RF MEMS) capacitive switches is reported by considering two key aspects: (1) materials selection approaches for improving performance, and (2) fabrication methods used in capacitive MEMS switches. The beam and dielectric materials used in capacitive MEMS switches and the performance achieved through them are reviewed and reported by a rigorous literature survey. Further, materials selection approaches for the beam membrane and the dielectric layer are discussed using Ashby’s methodology, and other associated methods based on it, which uses material indices to evaluate the performance of a switch. Performance indicators for the beam materials selection are the pull-in voltage, RF loss, thermal residual stress, contact resistance, thermal conductivity, and maximum displacement, whereas the hold-down voltage, dielectric charging, leakage current, heat dissipation, capacitance ratio, and stability are performance indicators in dielectric materials selection. MEMS switch fabrication can be achieved through bulk micromachining processes and surface micromachining processes, but the surface micromachining process has been preferred over the last few decades. The fabricated MEMS switch components can be integrated using a monolithic complementary metal oxide semiconductor–micro-electromechanical systems (CMOS-MEMS) process for the realization of applications in sensors, resonators, amplifiers, phase shifters, and MEMS satellite vehicles for space applications. CMOS-MEMS monolithic fabrication is discussed further with the help of fabrication process involved and the process technology. The TSMC-CMOS 0.35 $$\upmu \hbox {m}$$
 technology is one of the leading technologies in CMOS-MEMS fabrication and is mainly used.

Khusbu Mehta

Papers

A novel capacitive RF-MEMS switch for multi-frequency operation