Piazza, Gianluca
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Publication Integrated Aluminum Nitride Piezoelectric Microelectromechanical System for Radio Front Ends(2009-06-29) Piazza, GianlucaThis article summarizes the most recent technological developments in the realization of integrated aluminum nitride (AlN) piezoelectric microelectromechanical system (MEMS) for radio frequency (rf) front ends to be employed in next generation wireless communication devices. The AlN-based resonator and switch technologies are presented, their principle of operation explained, and some key experimental achievements showing device operations between 20 MHz and 10 GHz are introduced. Fundamental material, device, and fabrication aspects that needed to be taken into account for the demonstration of the first integrated rf MEMS solution based on the combination of AlN MEMS resonators and switches are highlighted. Given the ability to operate over a broad range of frequencies on a single silicon chip, the AlN MEMS technology is extremely attractive for the demonstration of reconfigurable and multiband rf transceivers. Next generation rf architectures that take advantage of large scale integration of AlN MEMS resonators and switches are briefly presented.Publication One and Two Port Piezoelectric Higher Order Contour-Mode MEMS Resonators for Mechanical Signal Processing(2007-12-01) Piazza, GianlucaThis paper reports on the design, fabrication and testing of novel one and two port piezoelectric higher order contour-mode MEMS resonators that can be employed in RF wireless communications as frequency reference elements or arranged in arrays to form banks of multi-frequency filters. The paper offers a comparison of one and two port resonant devices exhibiting frequencies approximately ranging from 200 to 800 MHz, quality factor of few thousands (1000–2500) and motional resistances ranging from 25 to 1000 Ω. Fundamental advantages and limitations of each solution are discussed. The reported experimental results focus on the response of a higher order one port resonator under different environmental conditions and a new class of two port contour resonators for narrow band filtering applications. Furthermore, an overview of novel frequency synthesis schemes that can be enabled by these contour-mode resonators is briefly presented.Publication Nanoscaled Piezoelectric Aluminum Nitride Contour- Mode Resonant Sensors(2010-11-01) Piazza, Gianluca; Rinaldi, Matteo; Zuniga, ChiaraThis paper reports on a new class of nanoscaled piezoelectric aluminum nitride contour-mode resonant sensors (CMR-S) that have been developed for the gravimetric detection of volatile organic chemicals (VOC). The use of the CMR-S and its scaling for the making of large arrays of detectors is justified in terms of the superior sensitivity and limit of detection (LOD ~ zg/μm2) that this technology attains with respect to any other available acoustic device. The choice of a novel functionalization layer based on ss-DNA is introduced as an effective way to selectively detect multiple VOCs without altering the electromechanical characteristics of the resonator. Experimental results confirming the advantages of scaling the device dimensions and its frequency of operation in terms of improved LOD and measurement speed are presented. Furthermore, preliminary data showing selective detection of dymethyl-methylphosphonate (DMMP) and dinitroluene (DNT) (with LOD in the order of ppt) are reported.Publication Demonstration of Inverse Acoustic Band Gap Structures in AlN and Integration with Piezoelectric Contour Mode Transducers(2009-06-01) Kuo, Nai-Kuei; Zuo, Chengjie; Piazza, GianlucaThis paper presents the first design and demonstration of a novel inverse acoustic band gap (IABG) structure in aluminum nitride (AlN) and its direct integration with piezoelectric contour-mode transducers. The experimental results indicate that the IABG structure has a stop band from 185 MHz to 240 MHz and is centered around 219 MHz with maximum rejection of 30 dB. The ABG-induced phonon scattering causes a frequency band gap that prohibits the propagation of certain acoustic wavelengths. In this work, the IABG unit cell consists of a high acoustic velocity (V) center material, which is formed by 2-μm-thick AlN sandwiched by 200-nm-thick platinum (Pt) and is held by four thin tethers and surrounded by a low acoustic velocity material (air). This cell arrangement enlarges the frequency band gap and eases the requirements on the thickness (d) to lattice constant (a) ratio, which was imposed by previous ABG demonstration in the very high frequency range. The finite element method (FEM) analysis indicates that the IABG can produce a gap-to-midgap ratio of 13.5% even when the d/a ratio is as small as 0.23. This advantage further allows the direct integration of the IABG with high frequency bulk acoustic wave (BAW) transducers.Publication 5-10 GHz AlN Contour-Mode Nanoelectromechanical Resonators(2009-01-01) Rinaldi, Matteo; Zuniga, Chiara; Piazza, GianlucaThis paper reports on the design and experimental verification of Super High Frequency (SHF) laterally vibrating NanoElctroMechanical (NEMS) resonators. For the first time, AlN piezoelectric nanoresonators with multiple frequencies of operation ranging between 5 and 10 GHz have been fabricated on the same chip and attained the highest f-Q product (4.6E12 Hz) ever reported in AlN contour-mode devices. These piezoelectric NEMS resonators are the first of their class to demonstrate on-chip sensing and actuation of nanostructures without the need of cumbersome or power consuming excitation and readout systems. Effective piezoelectric activity has been demonstrated in thin AlN films having vertical and lateral features in the range of 250 nm.Publication Single-Chip Multiple-Frequency ALN MEMS Filters Based on Contour-Mode Piezoelectric Resonators(2007-04-01) Piazza, Gianluca; Stephanou, Philip J; Pisano, Albert PThis paper reports experimental results on a new class of single-chip multiple-frequency (up to 236 MHz) filters that are based on low motional resistance contour-mode aluminum nitride piezoelectric micromechanical resonators. Rectangular plates and rings are made out of an aluminum nitride layer sandwiched between a bottom platinum electrode and a top aluminum electrode. For the first time, these devices have been electrically cascaded to yield high performance, low insertion loss (as low as 4 dB at 93MHz), and large rejection (27 dB at 236 MHz) micromechanical bandpass filters. This novel technology could revolutionize wireless communication systems by allowing cofabrication of multiple frequency filters on the same chip, potentially reducing form factors and manufacturing costs. In addition, these filters require terminations (1 kOmega termination is used at 236 MHz) that can be realized with on-chip inductors and capacitors, enabling their direct interface with standard 50-Omega systems.Publication Dual-Beam Actuation of Piezoelectric AlN RF MEMS Switches Monolithically Integrated with AlN Contour-Mode Resonators(2008-09-01) Mahameed, Rashed; Sinha, Nipun; Pisani, Marcelo B; Piazza, GianlucaThis work reports on piezoelectric Aluminum Nitride (AlN) based dual-beam RF MEMS switches that have been monolithically integrated with AlN contour-mode resonators. The dual-beam switch design presented in this paper intrinsically compensates for the residual stress in the deposited films, requires low actuation voltage (5 to 20 V), facilitates active pull-off to open the switch and exhibits fast switching times (1 to 2 μs). This work also presents the combined response (cascaded S parameters) of a resonator and a switch that were co-fabricated on the same substrate. The response shows that the resonator can be effectively turned on and off by the switch. A post-CMOS compatible process was used for the co-fabrication of both the switches and the resonators. The single-chip RF solution presented herein constitutes an unprecedented step forward towards the realization of compact, low loss and integrated multi-frequency RF front-ends.Publication Novel Electrode Configurations in Dual-Layer Stacked and Switchable AlN Contour-Mode Resonators for Low Impedance Filter Termination and Reduced Insertion Loss(2010-01-01) Zuo, Chengjie; Sinha, Nipun; Piazza, GianlucaThis paper reports, for the first time, on the design and demonstration of two novel electrode configurations in dual-layer stacked Aluminum Nitride (AlN) piezoelectric contour-mode resonators to obtain low filter termination resistance (down to 300 Ω, which also results in better filter out-of-band rejection) and reduced insertion loss (IL as low as 1.6 dB) in multi-frequency (100 MHz – 1 GHz) AlN MEMS filters. The microfabrication process is fully compatible with the previously demonstrated AlN RF MEMS switches, which makes it possible to design and integrate multi-frequency switchable filter banks on a single chip.Publication Super-High-Frequency Two-Port AlN Contour-Mode Resonators for RF Applications(2010-01-01) Rinaldi, Matteo; Zuniga, Chiara; Zuo, Chengjie; Piazza, GianlucaThis paper reports on the design and experimental verification of a new class of thin-film (250 nm) superhigh- frequency laterally-vibrating piezoelectric microelectromechanical (MEMS) resonators suitable for the fabrication of narrow-band MEMS filters operating at frequencies above 3 GHz. The device dimensions have been opportunely scaled both in the lateral and vertical dimensions to excite a contourextensional mode of vibration in nanofeatures of an ultra-thin (250 nm) AlN film. In this first demonstration, 2-port resonators vibrating up to 4.5 GHz have been fabricated on the same die and attained electromechanical coupling, kt^2, in excess of 1.5%. These devices are employed to synthesize the highest frequency MEMS filter (3.7 GHz) based on AlN contour-mode resonator technology ever reported.Publication Use of a Single Multiplexed CMOS Oscillator as Direct Frequency Read-Out for an Array of Eight AlN Contour-Mode NEMS Resonant Sensors(2010-11-01) Rinaldi, Matteo; Zuniga, Chiara; Duick, Brandon; Piazza, GianlucaThis paper reports on the first demonstration of a single multiplexed CMOS oscillator circuit employed as direct frequency readout for an array of 8 nanoscaled aluminum nitride Contour-Mode Resonant Sensors (CMR-S). In this first prototype 8 thin-film (250 nm) AlN CMR-S operating at 186 MHz were fabricated on the same chip and simultaneously wire-bonded to a Pierce-like oscillator circuit (fabricated in the ON Semiconductor 0.5 µm CMOS process) by means of 8 CMOS transmission gates addressed via a 3 bit on-chip decoder. The 8 CMR-S were simultaneously exposed to different concentrations of methanol (0.1–1% of the saturated vapor pressure) and their response was monitored in a time-multiplexed mode. Frequency shifts of 300 Hz corresponding to changes of mass per unit area of 7 ag/µm2 were experimentally detected. Values of phase noise derived Allan deviation as low as 0.9 Hz were measured. Such Allan deviation translates in an estimated limit of detection of 21 zg/µm2.