David Mardivirin

Charging in Dielectricless Capacitive RF-MEMS Switches

This paper presents results on high lifetime RF microelectromechanical (RF-MEMS) dielectricless capacitive switches. Using air gap variation only, these RF MEMS capacitive switches achieve a capacitance ratio of 9, associated with small residual charging. The reliability of the switch has been studied, pull-in and pull-out voltages shifts have been observed, modeled and validated with good agreement between model and measurements for a switch held for one month in the down state. The dependence of charging mechanism to the biasing signal is also presented by applying unipolar and bipolar waveforms with different duty cycles. Charging can be modeled using a simple Curie-Von Schweidler equation. It is shown that the duty cycle of the bias signal is strongly accelerating switch failure, and that using bipolar signals improves the lifetime of these switches by several orders of magnitude. The projected lifetime of current RF-MEMS dielectricless switches held in the down state using bipolar signals is several tens of years.

Voltage and current-activated metal-insulator transition in VO2-based electrical switches : a lifetime operation analysis

Abstract Vanadium dioxide is an intensively studied material that undergoes a temperature-induced metal–insulator phase transition accompanied by a large change in electrical resistivity. Electrical switches based on this material show promising properties in terms of speed and broadband operation. The exploration of the failure behavior and reliability of such devices is very important in view of their integration in practical electronic circuits. We performed systematic lifetime investigations of two-terminal switches based on the electrical activation of the metal–insulator transition in VO2 thin films. The devices were integrated in coplanar microwave waveguides (CPWs) in series configuration. We detected the evolution of a 10 GHz microwave signal transmitted through the CPW, modulated by the activation of the VO2 switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO2-based switching (more than 260 million cycles without failure) compared with the voltage-activated mode (breakdown at around 16 million activation cycles). The evolution of the electrical self-oscillations of a VO2-based switch induced in the current-operated mode is a subtle indicator of the material properties modification and can be used to monitor its behavior under various external stresses in sensor applications.

Split Ring Resonators (SRRs) Based on Micro-Electro-Mechanical Deflectable Cantilever-Type Rings: Application to Tunable Stopband Filters

A new principle for the implementation of tunable split ring resonators (SRRs) is presented. The rings forming the SRRs are partly fixed to the substrate (anchor) and partly suspended (up-curved cantilever). Through electrostatic actuation, the suspended parts are deflected down, the distributed capacitance between the pair of coupled rings is modified, and hence the resonance frequency of the SRR can be electrically tuned. To obtain electrically movable rings, a cantilever-type micro-electro-mechanical-system (MEMS) design and fabrication process is applied. The resonance frequencies at the different switching states are measured by coupling the tunable SRR to a host microstrip line, and reveal that significant tuning ranges can be achieved. This novel tuning concept is applied to the implementation of tunable stopband filters at Ku band as proof-of-concept demonstrators.

Study of Residual charing in dielectric less capacitive MEMS switches

Dielectric charging is one of the most challenging issues in RF-MEMS capacitive switches. Dielectric less capacitive switch is shown with a measured on to off ratio of 9. The reliability of the switch has been studied and residual pull in voltage shift has been observed. For the first time, charging results are presented on this type of switch and validated up to one month. It is shwon that charging can be modeled using a simple Curie-Von Schweidler equation. This model has been validated, with good agreement between the coefficients determined after holding down the switch for about 10000 s, and further experimenal results up to one month in the down state.

Ku band DMTL medium power phase shifters

The first part of this paper deals with curled shunt capacitive MEMS switched varactors with good power handling capabilities. These devices have been able to achieve 1 billion cycles under 5 W in hot switching conditions. These cantilevers have been used as switched capacitors periodically loaded along a Coplanar Wave Guide (CPW) line to form a Distributed MEMS Transmission Line (DMTL) phase shifter. In the second part, the integration of these beams in 90° and 180° DMTL sections operating at 15 GHz is shown. For these respective configurations, phase shifts of 89.3° and 178° have been observed and validate this conception. With reasonable loss of 60°/dB, these devices are among the first MEMS based phase shifter in literature able to operate at such power level in hot switching conditions.

Charging acceleration in dielectric less RF MEMS switched varactors under CW microwave power

The effect of microwave power on charging of dielectric less switches is presented and related to temperature elevation. We demonstrate operation under 6.3 Watts CW operation and an estimation of the switch temperature under 50% duty cycle bipolar bias. It is shown that the switch is following accelerated charging with similar time evolution than under low power, and that the switch temperature reaches about 60°C under 6.3W CW of applied microwave signal

Zero level metal thin film package for RF MEMS

Because they have moving parts, and they need to work in a specific atmosphere (vacuum, inert gas…), micro-electromechanical system (MEMS) are not compatible with integrated circuit packaging technologies. So, in order to accelerate commercialization of RF MEMS devices, the development of packaging technologies is one of the most critical issues that should be solved. A process has been developed to effectively package RF MEMS switches using a technique called wafer level thin film micro encapsulation. This technology is designed to be compatible with high performance RF MEMS ohmic switch fabrication.