Chiara Zuniga

Super-high-frequency two-port AlN contour-mode resonators for RF applications

This 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 contour-extensional 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.

5-10 GHz AlN Contour-Mode Nanoelectromechanical Resonators

This 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 (~ 4.6· 1012 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.

Nanoenabled microelectromechanical sensor for volatile organic chemical detection

A nanoenabled gravimetric chemical sensor prototype based on the large scale integration of single-stranded DNA (ss-DNA) decorated single-walled carbon nanotubes (SWNTs) as nanofunctionalization layer for aluminum nitride contour-mode resonant microelectromechanical (MEM) gravimetric sensors has been demonstrated. The capability of two distinct single strands of DNA bound to SWNTs to enhance differently the adsorption of volatile organic compounds such as dinitroluene (simulant for explosive vapor) and dymethyl-methylphosphonate (simulant for nerve agent sarin) has been verified experimentally. Different levels of sensitivity (17.3 and 28 KHz μm2/fg) due to separate frequencies of operation (287 and 450 MHz) on the same die have also been shown to prove the large dynamic range of sensitivity attainable with the sensor. The adsorption process in the ss-DNA decorated SWNTs does not occur in the bulk of the material, but solely involves the surface, which permits to achieve 50% recovery in less than 29 s.

Ss-DNA functionalized array of ALN Contour-Mode NEMS Resonant Sensors with single CMOS multiplexed oscillator for sub-ppb detection of volatile organic chemicals

This paper reports on the design and experimental verification of the first prototype of a resonant sensing platform based on nanoscaled aluminum nitride Contour-Mode Resonant Sensors (CMR-S) for selective detection of sub-ppb levels of volatile organic chemicals (VOCs). For the first time arrays of 8 nano-CMR-S were fabricated on the same chip and functionalized with two different thiol-terminated ss-DNA sequences. A low noise and low power (as low as 224 µW) CMOS circuit read-out capable of monitoring the responses of each NEMS sensor in a time-multiplexed mode was used. A ss-DNA sequence dependant adsorption of two vapors, such as DNT and DMMP, was recorded. Concentrations of DMMP and DNT as low as 700 part per billion (ppb) and 700 part per trillion (ppt), respectively, were experimentally detected. A limit of detection to mass per unit area as low as ∼60 zg/µm2 was extracted by noise characterization of the sensor array.

AlN contour-mode resonators for narrow-band filters above 3 GHz

This paper reports on the design and experimental verification of a new class of thin-film (250 nm) Super High Frequency (SHF) 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 in order to excite a contour-extensional mode of vibration in nano features of an ultra-thin (250 nm) Aluminum Nitride (AlN) film. In this first demonstration two-port resonators vibrating up to 4.5 GHz were fabricated on the same die and attained electromechanical coupling, kt2, in excess of 1.5 %. These devices were employed to synthesize the highest frequency ever reported MEMS filter (3.7 GHz) based on AlN contour-mode resonator (CMR) technology.

Ultra-thin-film AlN contour-mode resonators for sensing applications

This paper reports on the design and experimental verification of a new class of ultra-thin-film (250 nm) aluminum nitride (AlN) microelectromechanical system (MEMS) contour-mode resonators (CMRs) suitable for the fabrication of ultra sensitive gravimetric sensors. The device thickness was opportunely scaled in order to increase the mass sensitivity, while keeping a constant frequency of operation. In this first demonstration the resonance frequency of the device was set to 178 MHz and a mass sensitivity as high as 38.96 KHz·µm2/fg was attained. This device demonstrates the unique capability of the CMR technology to decouple resonance frequency from mass sensitivity.

Gravimetric chemical sensor based on the direct integration of SWNTS on ALN Contour-Mode MEMS resonators

This paper reports on the first demonstration of a gravimetric chemical sensor based on direct integration of single wall carbon nanotubes (SWNTs) grown by chemical vapor deposition (CVD) on AIN contour-mode MicroElectroMechanical (MEMS) resonators. In this first prototype the ability of SWNTs to readily adsorb volatile organic chemicals has been combined with the capability of AIN Contour-Mode MEMS resonator to provide for different levels of sensitivity due to separate frequencies of operation on the same die. Two devices with resonance frequencies of 287 MHz and 442 MHz have been exposed to different concentrations of DMMP in the range from 80 to 800 ppm. Values of mass sensitivity equal to 1.8 KHz/pg and 2.65 KHz/pg respectively have been measured.

High frequency AlN MEMS resonators with integrated nano hot plate for temperature controlled operation

This paper presents the design and experimental verification of the first MEMS resonator ovenized by means of an integrated nano hot plate suspended over the micromechanical resonant element. This first prototype is formed by a composite structure in which a fully anchored Aluminum Nitride (AlN) Lateral Field Excited-Floating (LFE-F) Contour-Mode MEMS resonator (CMR) and a nanoscale heating element are perfectly overlapped and separated by a sub-micron air gap. The placement of the heating element outside the body of the resonator, but suspended over it, allowed maintaining the electromechanical properties of the device unchanged (same kt2·Q compared to the non-ovenized case). This resulted in a 968 MHz ovenized microresonator with quality factor, Q, of ~1800, electromechanical coupling coefficient, kt2, of ~0.9% and motional resistance, Rm, of ~50 Ω. At the same time, efficient ovenization of the MEMS resonator (CMR temperature rise factor of 18.3 K/mW) is achieved by scaling the dimensions of the heating element (i.e. implementing a nano hot plate) and minimizing the air gap between the resonator and the heater.

Use of a single multiplexed CMOS oscillator as direct frequency read-out for an array of eight AlN Contour-Mode NEMS Resonant Sensors

This 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.

Ultra-thin Super High Frequency two-port ALN contour-mode resonators and filters

This paper reports on the demonstration of a new class of ultra-thin (250 nm thick) Super High Frequency (SHF) AlN piezoelectric two-port resonators and filters. A thickness field excitation scheme was employed to excite a higher order contour extensional mode of vibration in an AlN nano plate (250 nm thick) above 3 GHz and synthesize a 1.96 GHz narrow-bandwidth channel-select filter. The devices of this work are able to operate over a frequency range from 1.9 to 3.5 GHz and are employed to synthesize the highest frequency MEMS filter based on electrically self-coupled AlN contour-mode resonators. Very narrow bandwidth (∼ 0.35%) and high off-band rejection (∼ 35 dB) were achieved at an operating frequency of 1.96 GHz. This first prototype showed insertion loss of 11 dB, which can be improved to few dB if parasitic elements are eliminated or device capacitance is increased.