G. Murillo

Integration of RF-MEMS resonators on submicrometric commercial CMOS technologies

Integration of electrostatically driven and capacitively transduced MEMS resonators in commercial CMOS technologies is discussed. A figure of merit to study the performance of different structural layers and different technologies is defined. High frequency (HF) and very high frequency (VHF) resonance MEMS metal resonators are fabricated on a deep submicron 0.18 µm commercial CMOS technology and are characterized using electrical tests without amplification, demonstrating the applicability of the MEMS fabrication process for future technologies. Moreover, the fabricated devices show comparable performance in terms of Q × fres with previously presented MEMS resonators, whereas the small gap allows obtaining a low motional resistance with a single resonator approach.

A CMOS–MEMS RF-Tunable Bandpass Filter Based on Two High-

This letter presents the design, fabrication, and demonstration of a CMOS-MEMS filter based on two high-Q submicrometer-scale clamped-clamped beam resonators with resonance frequency around 22 MHz. The MEMS resonators are fabricated with a 0.35-mum CMOS process and monolithically integrated with an on-chip differential amplifier. The CMOS-MEMS resonator shows high-quality factors of 227 in air conditions and 4400 in a vacuum for a bias voltage of 5 V. In air conditions, the CMOS-MEMS parallel filter presents a programmable bandwidth from 100 to 200 kHz with a <1-dB ripple. In a vacuum, the filter presents a stop-band attenuation of 37 dB and a shape factor as low as 2.5 for a CMOS-compatible bias voltage of 5 V, demonstrating competitive performance compared with the state of the art of not fully integrated MEMS filters.

Q

A novel technique for global packaging of MEMS devices using standard CMOS technology is presented. A MEMS polysilicon resonator is fabricated and on-chip packaged using two metal layers already available from the CMOS technology. A simple buffered HF wet etching process is performed in house to release the MEMS resonator while metal deposition is used to vacuum seal the zero-level package. Both post-processing steps are carried out on CMOS chips. The design of the metal layers is carefully done in order to avoid the degradation of the MEMS. The electrical frequency response of the resonator is used for testing the performance of the final package. Electrical measurements and physical characterization demonstrate proper performance of the MEMS resonator and package.

22-MHz Polysilicon Clamped-Clamped Beam Resonators

Clamped-clamped beam resonators are designed and fabricated in a 0.35µm CMOS commercial technology, using a simple one-step mask-less wet etching to release the MEMS structures. The resonator, with a 22MHz resonance frequency shows a Q value of 227 and 4400, when measured at atmospheric pressure and vacuum, respectively. This resonator is used as the main building block for filtering application. Using parallel filtering and differential on-chip CMOS amplification, the RF-CMOS-MEMS system forms a tunable band-pass filter with programmable bandwidth (from 100kHz to 200kHz), stop band rejections of 30 dB and shape factors at −20dB smaller than 3, providing comparable performance than other MEMS filters using specific technologies.

Zero-level packaging of MEMS in standard CMOS technology

Abstract This work introduces a novel concept for energy scavenging from ambient vibrations utilizing ZnO nanowires (NWs). This concept relies on the combination into a single device of a resonant element (i.e. an inertial mass suspended by four serpentine springs) and two arrays of NWs grown at both sides of the inertial mass. The NWs can be bent as a result of the resonant motion of the mass. Due to the zigzag-shaped profile of the inertial mass, this bending generates an electric current between the electrodes. This power can be used to supply wireless sensor nodes at the micro and nanoscale level. In addition, this generator can be integrated with other elements that can be achieved by taking advantage of the ZnO NWs and their unique properties such as chemical sensors, optoelectromechanical systems or logic circuits driven by mechanical or optical signals. A detailed fabrication process, containing the NW growth method, is described in this paper. Theoretical calculations and FEM simulations have been performed and show the possibility of using these kinds of devices to scavenge energy from sonic and ultrasonic waves.

High Q CMOS-MEMS resonators and its applications as RF tunable band-pass filters

A double-ended tuning fork (DETF) fabricated in a 0.35 um commercial CMOS technology is presented. Resonator performance for the application of this device in a RF front-end is measured using electrical test. DEFT offers a higher isolation between ports than clamped -clamped beams and the possibility to create a band-pass for frequency filtering or mixing using a single resonator. Discrepancies between expected and obtained results are studied using FEM mechanical simulations.

Hybrid resonant energy harvester integrating ZnO NWs with MEMS for enabling zero-power wireless sensor nodes

The electric power output of a piezoelectric nanogenerator (PENG) depends on the various physical parameters of the constituent materials, including the piezoelectric coefficient, Young’s modulus, and dielectric constant. Herein, we report the mechanical and electrical properties of a poly(vinylidene fluoride)–BaTiO3 (PVDF–BTO) composite-based PENG. Variation of the BTO nanoparticle (NP) content enabled the systematic tuning of the physical parameters that are related to power generation in the composite. The Young’s modulus of the PVDF–BTO composite initially increased, and then eventually decreased, with the increasing BTO content, which was probably due to the clustering effect of the high modulus BTO NPs. The dielectric constant of the composite continuously increased as the BaTiO3 content increased. The piezoelectric outputs were greatly enhanced at 10 wt% of BTO, where the Young’s modulus was the highest. These results indicate that the Young’s modulus plays an important role in the piezoelectric power generation of the composite-based PENGs.

Double-ended tuning fork resonator in 0.35um CMOS technology for RF applications

In this paper, the transduction part of a vibration-driven piezoelectric energy harvester has been designed, fabricated and characterized. The fabrication technology used allows the monolithic integration of Film Bulk Acoustic Resonators (FBARs) in the same wafer. This piezoelectric-based system together with an integrated circuitry can contain all the elements of a node that can belong to a wireless sensor network (WSN). A scavenged power of around 0.2 μW, i.e. an power density of around nd 0.13 mW/cm3, can be extracted at a resonance frequency of 515 Hz and an input acceleration of 0.64 m/s2.