Montserrat Fernandez-Bolanos

Steep slope VO 2 switches for wide-band (DC-40 GHz) reconfigurable electronics

This work proves the feasibility of electrically actuated, CMOS compatible, microwave VO₂ switches on SiO₂/Si substrates with low variability, 100% yield, better than 109 cycles lifetime, ultra-steep OFF-ON transition and better RF performance than previously reported VO₂ switches on Al₂O₃ substrates (flat -0.6 dB S_21-ON with -10 dB S_21-OFF at 40 GHz). The extensive characterization of the fabricated switches has led to an optimum design with maximized S_21-ON/S_21-OFF ratio and validation as a promising solution for wideband reconfigurable electronics.

Reliability of RF MEMS Capacitive Switches and Distributed MEMS Phase Shifters using AlN Dielectric

The reliability and charging/discharging dynamics of wideband (1.5-14GHz) phase shifters made of MEMS capacitive switches using Aluminum Nitride (AlN) as dielectric are originally reported. Phase shifter lifetimes exceeding 109 cycles are achieved in hot-cycling (+5dBm RF power). Dynamic tests were done for the first time under ambient conditions (50% humidity) over 2×109 cycles with no major degradation of individual switches performances. It is demonstrated that the phase shifter is very robust (no permanent failure or stiction) and can withstand environmental effects as well as high temperature variations, without the need of expensive hermetical packaging. The excellent reliability is attributed to the slow dielectric charging (a square-root time law) and fast discharging mechanism of AlN (an exponential time law proposed and validated in our work). We extend the validity of charging and discharging models from single device to arrays of parallel MEMS capacitors.

Amorphous carbon active contact layer for reliable nanoelectromechanical switches

This paper reports an amorphous carbon (a-C) contact coating for ultra-low-power curved nanoelectromechanical (NEM) switches. a-C addresses important problems in miniaturization and low-power operation of mechanical relays: i) the surface energy is lower than that of metals, ii) active formation of highly localized a-C conducting filaments offers a way to form nanoscale contacts, and iii) high reliability is achieved through the excellent wear properties of a-C, demonstrated in this paper with more than 100 million hot switching cycles. Finally, a full inverter using a-C contacts is fabricated to demonstrate the viability of the concept.

Analytical Compact Model in Verilog-A for Electrostatically Actuated Ohmic Switches

Nowadays, electronics face a challenge regarding the power consumption of integrated circuits (ICs). There is a need for new devices that can provide improved switching capabilities. The downscaled electrostatically actuated ohmic switch, as a (re)emerging device, is a promising candidate to meet this need. To bring such a device seamlessly into IC design, it must be accompanied by an accurate, fast and robust analytical compact model. The development and the main characteristics of such a model are described within this paper. Extensive numerical simulations and measurements have been used to validate the model.

3D heterogeneous integration for novel functionality

Keywords: heterogeneous integration, through silicon vias, radio frequency, photonic, energy harverting ; e-BRAINS Reference EPFL-CONF-174872doi:10.1109/3DIC.2010.5751423 Record created on 2012-02-13, modified on 2017-05-10

Tunable capacitors and microwave filters based on vanadium dioxide metal-insulator transition

We report the fabrication, modeling and characterization of novel microwave tunable capacitors based on the metal-insulator transition (MIT) of Vanadium Dioxide (VO2). We present the advantages of VO2-based capacitors over alternative technologies for microwave reconfigurable electronics in terms of ease of integration, design and performance at high frequency. We show the potential of the proposed devices for RF reconfigurable electronics by fabricating a tunable bandstop filter (22.5-19.8 GHz) with insertion loss <; 2 dB up to 40 GHz.

Fine pitch 3D-TSV based high frequency components for RF MEMS applications

The development of interconnections suitable for radio-frequency (RF) and millimeter-wave (mm-wave) applications is of foremost importance for the feasibility of high-quality substrate-integrated devices. For this purpose, we introduce and validate the technology to implement fine-pitch high-aspect ratio tungsten-filled through-silicon vias (W-TSVs) adapted for high-frequency applications. The presented technology is optimized for integration with RF MEMS, for which we propose a compatible fabrication process flow. We designed and characterized RF test structures to assess the quality of the W-TSVs and their suitability for radio-frequency integrated circuits (RFIC) applications, showing low insertion loss for TSV in coplanar waveguides (CPW) and high-performance wideband mm-wave antennas.

Scalable conformal array for multi-gigabit body centric wireless communication

In this work a conceptual design of a conformal antenna array is presented for a millimeter-wave antenna system, optimized for low-cost mass production in PCB technology. The conformal array is constituted by four cube faces with two antennas realized on each face. A printed circuit board (PCB) laminate material was chosen for developing this integrated 60 GHz antenna solution. The beamforming capabilities of the 1 × 8 antenna array were validated using similar array topology but at frequency of 17.2 GHz. The proposed array enables the formation of a steerable high gain beam, significantly compensating the channel loss or shadowing in body area network (BAN), thus offering more robust, higher speed performance. The array topology is easily scalable and the antenna gain up till 12.2 dB is reachable. On one side such high gain combined with an agile beam steering is a significant power saving solution for RF front-end. On the other side a use of 60 GHz frequency band makes the antenna array extremely small and thus easily embeddable into wearable medical or commercial devices.

Thermally Stable Distributed MEMS Phase Shifter for Airborne and Space Applications

This paper presents an in-depth study of the design, modelling, circuit parameter extraction and characterization of a distributed MEMS digital microwave phase shifter. Bridge-type digital capacitors periodically loaded on a 5 mm CPW (with an actuation voltage of 22 V) has been fabricated and successfully measured in a wide range of frequencies (1-14 GHZ), achieving a true-time delay of 25 ps. Experimental data are in very good agreement with the equivalent circuit model and high frequency 3D EM simulations for both single switches and phase shifters. These phase shifters are designed for beam steering applications in airborne and space which require operation within large range of temperatures. Therefore, temperature measurements fulfilling the applications requirements have been done in vacuum and in room air from -130degC to 50degC. It is demonstrated that the delay deviation of our phase shifter is 10% (2 ps) at 14 GHz for the full temperature range (DeltaTdeg=180deg).

Capacitive pressure microsensor fabricated by bulk micromachining and sacrificial layer etching

A new capacitive silicon pressure sensor fabricated by a combination of bulk and surface micromachining is presented. The sensor is composed of a polysilicon membrane that deflects due to the pressure difference applied over it. Its main advantages are a simple fabrication process and an efficient integrability with other devices. The behaviour of the sensor, obtained by mathematical modeling of the membrane deflection is presented, along with the numerical simulations that provide the characteristic curves. From these results, a study on how geometry affects sensor performance is deduced. Results obtained are in good agreement with previous similar devices