Gabriel Vidal-Álvarez

3-terminal tungsten CMOS-NEM relay

The present work describes the design, fabrication and experimental results of a 3-terminal laterally actuated tungsten nanoelectromechanical (NEM) relay which is monolithically integrated in a 0.35 μm commercial standard CMOS technology. The movable structure is released by means of a simple one-step maskless wet etching. The switch shows an abrupt switching with less than 5 mV/decade and a good on-off current ratio of - 104 although it exhibits an on-state contact resistance RON around 500 MΩ. Also, the relay is cycled up to 1500 times in ambient conditions showing great endurance but variability in its contact.

Top-down silicon microcantilever with coupled bottom-up silicon nanowire for enhanced mass resolution

A stepped cantilever composed of a bottom-up silicon nanowire coupled to a top-down silicon microcantilever electrostatically actuated and with capacitive or optical readout is fabricated and analyzed, both theoretically and experimentally, for mass sensing applications. The mass sensitivity at the nanowire free end and the frequency resolution considering thermomechanical noise are computed for different nanowire dimensions. The results obtained show that the coupled structure presents a very good mass sensitivity thanks to the nanowire, where the mass depositions take place, while also presenting a very good frequency resolution due to the microcantilever, where the transduction is carried out. A two-fold improvement in mass sensitivity with respect to that of the microcantilever standalone is experimentally demonstrated, and at least an order-of-magnitude improvement is theoretically predicted, only changing the nanowire length. Very close frequency resolutions are experimentally measured and theoretically predicted for a standalone microcantilever and for a microcantilever-nanowire coupled system. Thus, an improvement in mass sensing resolution of the microcantilever-nanowire stepped cantilever is demonstrated with respect to that of the microcantilever standalone.

The influence of the parasitic current on the nonlinear electrical response of capacitively sensed cantilever resonators

The influence of the parasitic feedthrough current on the nonlinear electrical response of capacitively sensed cantilever resonators is analyzed theoretically and experimentally. We show that the parasitic current strongly affects the shape of the nonlinear electrical frequency response of such devices. Specifically, we demonstrate that in the electrical measurement, the directions of the jumps from the different transitions between branches of stable solutions depend on the parasitic current and are independent of the jumps directions in the mechanical domain. As a consequence, the nonlinear electrical frequency response of cantilevers with capacitive readout presents three different hysteretic cycle topologies: counterclockwise, bow tie, and clockwise. This is in contrast with the only one topology (counterclockwise) that appears in the nonlinear mechanical frequency response.

Dynamic Properties of Three-Terminal Tungsten CMOS-NEM Relays Under Nonlinear Tapping Mode

In this paper, we present the electrical characterization of the nonlinear tapping mode of the nanorelays capacitively transduced. Such a characterization is carried out utilizing three-terminal tungsten CMOS-NEM relays. Exciting electrostatically the switching devices near its resonance and detecting its movement by means of capacitive detection, we reveal double-side frequency dynamic-contact characteristics when the displacement is large and the tapping occur in the nonlinear regime. In this way, we take advantage of this periodic contact to evaluate the switching characteristics of the device. We report that the switch stands more than 10 billion of tapping cycles (in a cold switching scenario) without showing any failure. Moreover, we measure current-voltage (I-V) curves before and after the cycling test in order to evaluate the changes produced in the ON-state contact resistance and in the pull-in and pull-out voltages. This test reveals that the characterized switch has a consistent and repetitive pull-in voltage without changing its elastic properties. In addition, we observe that the pull-out voltage decreases slightly and the contact resistance diminishes (from an initial value of 2 GΩ to a minimum value of 735 MΩ. We eventually attribute this result to the fact that the superficial oxide is broken down due to the continuous tapping of the cantilever tip on the contact electrode.

CMOS-NEM relay based on tungsten VIA layer

A CMOS-NEM tungsten relay based on a 3-T configuration for logic applications is presented. The relay is integrated monolithically in the BEOL of a standard CMOS technology (AMS 0.35 μm) using the tungsten VIA3 layer. The relay is designed and fabricated during the CMOS process and released by a one-step mask-less wet etching. The measured devices show an essentially zero leakage current and a subthreshold slope less than 5 mV/decade with a 104 ratio between on-off current, although they exhibit a high contact resistance (~ 108 Ω). A cycling test was carried out up to 1800 cycles in ambient conditions. Throughout this test, the switch shows great endurance. Finally, the frequency response was also measured.

The influence of the parasitic current on the nonlinear electrical response of capacitive sensed cantilever beams

The influence of the parasitic current on the nonlinear electrical response of capacitive sensed cantilever beams is analyzed both theoretically and experimentally. We show that the parasitic current strongly affects the shape of the nonlinear electrical response of the aforementioned devices. Specifically, we demonstrate that in the electrical measurement, the direction of the jumps from the different transitions between branches of stable solutions, depend on the value of the parasitic current and is independent of the direction of the jump in the mechanical domain.

Nonlinear behavior of the capacitively coupled NEMS resonator operating close to the nonlinear regime cancellation

In this paper we present a 0-level package NEMS-on-CMOS resonator developed at SilTerra (Malaysia) for low cost frequency references. The characterization of the capacitively coupled resonator shows the coexistence of high order nonlinear terms that, close to the Duffing nonlinear terms cancellation, allows the simultaneous appearance of both, the mechanical and the electrical nonlinear regime. From the open loop characterization, we can conclude that there is an optimum biasing point close to the nonlinear regime cancellation where the power handling of the NEMS can be maximized. At the same time, a study of the frequency-amplitude evolution has shown that it is possible to obtain an operation point beyond the critical point where the resonance frequency does not depend of the amplitude fluctuations locally.

Fabrication and Measurement of a Suspended Nanochannel Microbridge Resonator Monolithically Integrated with CMOS Readout Circuitry

We present the fabrication and characterization of a suspended microbridge resonator with an embedded nanochannel. The suspended microbridge resonator is electrostatically actuated, capacitively sensed, and monolithically integrated with complementary metal-oxide-semiconductor (CMOS) readout circuitry. The device is fabricated using the back end of line (BEOL) layers of the AMS 0.35 μm commercial CMOS technology, interconnecting two metal layers with a contact layer. The fabricated device has a 6 fL capacity and has one of the smallest embedded channels so far. It is able to attain a mass sensitivity of 25 ag/Hz using a fully integrable electrical transduction.

A further study of reduced-order modeling techniques for nonlinear MEMS beams

This paper gives a further look at reduced-order modeling (ROM) techniques that can be applied to MEMS beams subject to nonlinear forces. It is focused on the popular method which consists in multiplying the equation governing the displacement of the beam by the displacement-dependent denominator of the nonlinear (electrostatic) force before modal projection is performed. Having already shown that in the case of 1-mode, 1-harmonic analysis, this method can lead to dramatically wrong results, we propose another choice of multiplicative coefficient, with much improved behavior. This method is illustrated, discussed and compared to other approaches in terms of simplicity, accuracy and range of validity.

Enhancement of higher harmonics detectability in a nonlinear nanoresonator

In this work we present a signature of frequency stabilization in a nonlinear regime for a clamped-clamped beam nanoresonator which would be a way to solve the problems of degradation of the resonance frequency in nanoresonators due to their nonlinear response.