High-Aspect-Ratio SOI Vibrating Micromechanical Resonators and Filters

Ayazi, Farrokh; Pourkamali, Siavash; Ho, G.K.; Abdolvand, Reza

doi:10.1109/mwsym.2006.249705

Cited by 13 publications

(8 citation statements)

References 12 publications

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“…The high motional resistance of several hundred kΩ to several MΩ is ascribed to the limited electromechanical coupling coefficient of the capacitive transduction. There are several methods to decrease the motional resistance, such as decreasing the spacing gap 43 , filling the gap with high-κ solid dielectric materials 44,45 , and increasing the transduction area 46 .…”

Section: Discussionmentioning

confidence: 99%

A Switchable High-Performance RF-MEMS Resonator with Flexible Frequency Generations

Chen

Kan

Yuan

et al. 2020

Sci Rep

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Resonators with multi-frequency generations at the device-level are highly desired in the future multiband, reconfigurable, and compact wireless communications. In this work, a switchable radio frequency micro-electro-mechanical system (RF-MEMS) resonator with multiple electrodes is presented. The resonator is designed to operate at the whispering gallery modes (WGMs). Simultaneous excitations of the second to seventh modes with high Q values are implemented within a single device using a pair of electrodes for driving and sensing. For effective multi-frequency excitations, the electrode span angle is optimized. The frequencies of the 37 μm and 18 μm-radius resonators range from 53 MHz to 176 MHz and 112 MHz to 366 MHz, respectively. The Q values in each mode are over 10 4 . Moreover, with the multi-electrode configurations, the specific mode can be enhanced with other modes suppressed. A more than 6 dB improvement of the spectrum peak is realized and the high Q values are maintained. A comprehensive theory is built up to clarify the driving/sensing principles under different electrode configurations. Furthermore, the air damping is found to have a significant effect on Q values for resonator with high stiffness vibrating in all the WGMs. The Q values in vacuum have at least two times improvement. The high-performance switchable resonator could dramatically reduce the power consumption, simplify the processing circuits, and occupy less footprint, which has great potential applications in future advanced RF front end systems.Future wireless communications, like 5 th generation (5 G) 1,2 , Internet of Thing (IOT) 3,4 , and tactile Internet 5 , urge for radio frequency (RF) front end transceivers with high operating frequencies, pronounced tunability and reconfigurability, reduced hardware redundancy and less power consumption 6 . Radio frequency micro-electro-mechanical system (RF-MEMS) technologies are emerging as an enabling solution to address the fast-growing demands of the advanced wireless communications 7-9 . MEMS resonators with remarkable characteristics of high f × Q products, high-level IC compatibility, small footprint, and low power consumption have great potential in communication applications, which are regarded as the key element to constitute the future RF front end transceivers 10-14 . Mechanically coupling high-Q MEMS resonators, MEMS filters with ultra-narrow passbands less than 0.1% and high stopband rejection over 50 dB have been demonstrated 15 , which are beneficial for the direct channel selection. Meanwhile, using MEMS resonators as frequency selection components, MEMS oscillators with low phase noise of −138 dBc/Hz @ 1 kHz 16 and excellent long-term frequency stability of ±0.1 ppm 17 have been implemented. The miniaturized MEMS oscillators are regarded as competitive alternatives of traditional off chip devices such as quartz crystals and surface acoustic wave (SAW) resonators 18 .Multi-frequency devices are highly desired to meet the requirements of wider frequency coverage 19 . Although...

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Section: Discussionmentioning

confidence: 99%

A Switchable High-Performance RF-MEMS Resonator with Flexible Frequency Generations

Chen

Kan

Yuan

et al. 2020

Sci Rep

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“…Interestingly, this defies the expectation of material loss theory [21]- [23], which predicts that the phononphonon interaction-constrained f · Q product of AlN material should only be about two times lower than that of silicon, with a theoretically expected Q on the order of 25,000 at 1 GHz [24]. Indeed, while measured Q's for polysilicon (e.g., Q = 161, 000 at 61.9 MHz [25]) or single-crystal silicon (e.g., Q = 77, 000 at 85.9MHz [26]) resonators have approached theoretical prediction, those for attached-electrode AlN resonators demonstrated so far fall far behind it. This large deviation is unlikely due to the difference between material properties of single-crystal AlN used for theory and sputtered AlN used in measurement, given the fact that the measured Q of a thickness-mode FBAR constructed of epitaxial singlecrystal AlN deposited at 1200-1300°C via MOCVD (Metal Organic Chemical Vapor Deposition) on a SiC wafer [27] is essentially the same Q∼1,000 as measured for FBARs constructed of sputtered AlN.…”

Section: Metal Electrode-induced Degradationmentioning

confidence: 99%

“…1 L m C m (26) Note that (25) increases as the air gap spacings increase. This upward frequency shift derives from the reactance change introduced by the air gaps [39] and should not be confused with the upward frequency shift caused by elimination of electrode mass loading when electrodes are separated from the piezoelectric material.…”

Section: Motional-to-static Capacitance Ratiomentioning

confidence: 99%

Capacitive-Piezoelectric Transducers for High-<inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> Micromechanical AlN Resonators

Hung

Nguyen

2015

J. Microelectromech. Syst.

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A capacitive-piezoelectric (also known as, capacitive-piezo) transducer that combines the strengths of capacitive and piezoelectric mechanisms to achieve a combination of electromechanical coupling and Q higher than otherwise attainable by either mechanism separately, has allowed demonstration of a 1.2-GHz contour-mode aluminum nitride (AlN) ring resonator with Q > 3000 on par with the highest measured d 31 -transduced AlN-only piezoelectric resonators past 1 GHz, and a 50-MHz disk array with an even higher Q > 12 000. Here, the key innovation is to separate the piezoelectric resonator from its metal electrodes by tiny gaps to eliminate metal material and metal-to-piezoelectric interface losses thought to limit thin-film piezoelectric resonator Q, while also maintaining high electric field strength to preserve a strong piezoelectric effect. While Q increases, electromechanical coupling decreases, but the k 2 eff · Q product can still increase overall. More importantly, use of the capacitive-piezo transducer allows a designer to trade electromechanical coupling for Q, providing a very useful method to tailor Q and coupling for narrowband radio frequency (RF) channel-selecting filters for which Q trumps coupling. This capacitive-piezo transducer concept does not require dc-bias voltages and allows for much thicker electrodes that reduce series resistance without mass loading the resonant structure. The latter is especially important as resonators and their supports continue to scale toward even higher frequencies.[2013-0395]

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“…Capacitive coupled-resonator filters have proved to be reliable in providing excellent selectivity fueled by minimal acoustic loss [1, 2]. Unfortunately, these devices usually suffer from high IL if terminated to 50 Ω.…”

Section: Introductionmentioning

confidence: 99%

High-frequency monolithic thin-film piezoelectric-on-substrate filters

Abdolvand

Ayazi

2009

Int. j. microw. wirel. technol.

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A class of micromachined acoustic filters is presented in which the number of individual resonant structures is reduced to 1 (monolithic filter). This resonant structure is comprised of a stack of thin-film piezoelectric-on-silicon. Symmetric and anti-symmetric resonance modes (dual modes) of the silicon structure are piezoelectrically excited and coupled to realize a 2-pole narrowband filter. High-order lateral bulk acoustic resonance modes of a rectangular plate are utilized to design dispersed-frequency UHF filters fabricated on a single substrate. Thickness mode filters are also realized at GHz frequencies using a new interdigitated electrode design. Additionally, it is shown that the filter bandwidth can be controlled by changing the dimensions of the resonant structure and the electrode pattern. Narrowband lateral mode filters with filter Q’s larger than 300 at ~440 MHz and thickness mode filters with filter Q’s in the range of 150–900 at ~3.1 GHz are demonstrated.

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High-Aspect-Ratio SOI Vibrating Micromechanical Resonators and Filters

Cited by 13 publications

References 12 publications

A Switchable High-Performance RF-MEMS Resonator with Flexible Frequency Generations

A Switchable High-Performance RF-MEMS Resonator with Flexible Frequency Generations

Capacitive-Piezoelectric Transducers for High-<inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> Micromechanical AlN Resonators

High-frequency monolithic thin-film piezoelectric-on-substrate filters

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