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

Surface roughness effects on electromechanical performance of RF-MEMS capacitive switches

Reliability of RF MEMS switches at cryogenic (liquid He) temperatures

\nPurposeThis paper aims to present an efficient design approach for the micro electromechanical systems (MEMS) accelerometers considering design parameters affecting the long-term reliability of these inertial sensors in comparison to traditional iterative microfabrication and experimental characterization approach.\n\n\nDesign/methodology/approachA dual-axis capacitive MEMS accelerometer design is presented considering the microfabrication process constraints of the foundry process. The performance of the MEMS accelerometer is analyzed through finite element method– based simulations considering main design parameters affecting the long-term reliability. The effect of microfabrication process induced residual stress, operating pressure variations in the range of 10 mTorr to atmospheric pressure, thermal variations in the operating temperature range of −40°C to 100°C and impulsive input acceleration at different input frequency values is presented in detail.\n\n\nFindingsThe effect of residual stress is negligible on performance of the MEMS accelerometer due to efficient design of mechanical suspension beams. The effect of operating temperature and pressure variations is negligible on energy loss factor. The thermal strain at high temperature causes the sensing plates to deform out of plane. The input dynamic acceleration range is 34 g at room temperature, which decreases with operating temperature variations. At low frequency input acceleration, the input acts as a quasi-static load, whereas at high frequency, it acts as a dynamic load for the MEMS accelerometer.\n\n\nOriginality/valueIn comparison with the traditional MEMS accelerometer design approaches, the proposed design approach focuses on the analysis of critical design parameters that affect the long-term reliability of MEMS accelerometer.\n

An efficient design of dual-axis MEMS accelerometer considering microfabrication process limitations and operating environment variations

The micro-electro-mechanical-system switch performance significantly depends on materials used for the design of different components. The two most important elements of the MEMS switch are the beam membrane and dielectric layer. Thus, the selection of a material for these two components should be done with utmost care. In this paper, Ashby’s material selection methodology is employed for choosing the best material for the beam membrane and dielectric layer by investigating a database of materials. The material indices for beam membrane selection are Young’s modulus, Poisson’s ratio, thermal coefficient, electrical resistivity, thermal conductivity, and fracture strength. To obtain the best dielectric material, hold down voltage, dielectric charging, thermal conductivity and stability are considered as material indices to get optimized performance in the switch. To validate the results of material selection using Ashby’s method, the top five selected materials for beam membrane and dielectric are applied on a MEMS switch and impacts of these materials on the electromechanical and RF performance have been presented. The results conclude that the Au and Al2O3 are preferred choice for beam membrane and dielectric material to offer good performance for the frequencies in the range of 50–100 GHz.

Investigations on beam membrane and dielectric materials using Ashby’s methodology and their impact on the performance of a MEMS capacitive switch

\n\nThe main challenge in the commercialization of the RF-MEMS switches is their reliability,\nrelated to both the electrical and mechanical domains. The development of test standards and understanding\nthe underlying physics of different failure modes has always been of major concern for the\nRF-MEMS designers. This paper reviews the different failure modes in the RF-MEMS switches like\nstiction, residual stress, cyclic fatigue, creep, wear and packaging in detail. The origin of these failure\nmodes, their characterization procedure and respective solutions presented in the literature are presented\nto get a better understanding of the state of the art work done in the field RF-MEMS reliability\nfor nearly past two decades.\n

Muhammad Mubasher Saleem and Hamid Nawaz

Papers

A Systematic Review of Reliability Issues in RF-MEMS Switches