scholarly journals Influence of Etching Trench on Keff2 of Film Bulk Acoustic Resonator

Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 102
Author(s):  
Chao Gao ◽  
Yang Zou ◽  
Jie Zhou ◽  
Yan Liu ◽  
Wenjuan Liu ◽  
...  
Keyword(s):  
Electromechanical Coupling ◽  
Great Influence ◽  
Acoustic Resonator ◽  
Superior Performance ◽  
Electromechanical Coupling Coefficient ◽  
Rf Filters ◽  
Acoustic Resonators ◽  
Rf Communication ◽  
Film Bulk Acoustic Resonators ◽  
Film Bulk

As radio-frequency (RF) communication becomes more ubiquitous globally, film bulk acoustic resonators (FBAR) have attracted great attention for their superior performance. One of the key parameters of an FBAR, the effective electromechanical coupling coefficient (Keff2), has a great influence on the bandwidth of RF filters. In this work, we propose a feasible method to tune the Keff2 of the FBAR by etching the piezoelectric material to form a trench around the active area of the FBAR. The influence of the position of the etching trench on the Keff2 of the FBAR was investigated by 3D finite element modeling and experimental fabricating. Meanwhile, a theoretical electrical model was presented to test and verify the simulated and measured results. The Keff2 of the FBAR tended to be reduced when the distance between the edge of the top electrode and the edge of the trench was increased, but the Q value of the FBAR was not degraded. This work provides a new possibility for tuning the Keff2 of resonators to meet the requirements of different filter bandwidths.

Selective Band Gap to Suppress the Spurious Acoustic Mode in Film Bulk Acoustic Resonator Structures

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Rafik Serhane ◽  
Fayçal Hadj-Larbi ◽  
Abdelkader Hassein-Bey ◽  
Abdelkrim Khelif
Keyword(s):  
Band Gap ◽  
Electromechanical Coupling ◽  
Lamb Waves ◽  
Phononic Crystal ◽  
Longitudinal Mode ◽  
Acoustic Resonator ◽  
Electromechanical Coupling Coefficient ◽  
Spurious Mode ◽  
Film Bulk Acoustic Resonator ◽  
Film Bulk

In this work, we investigate numerically the propagation of Lamb waves in a film bulk acoustic resonator (FBAR) structure formed by piezoelectric ZnO layer sandwiched between two Mo electrodes coupled with Bragg reflectors; the system is thus considered as a phononic-crystal (PnC) plate. The aim is to suppress the first-order symmetric Lamb wave mode considered as a spurious mode caused by the establishment of a lateral standing wave due to the reflection at the embedded lateral extremities of the structure; this spurious mode is superposing to the main longitudinal mode resonance of the FBAR. The finite element study, using harmonic and eigen-frequency analyses, is performed on the section of FBAR structure coupled with the PnC. In the presence of PnC, the simulation results show the evidence of a selective band gap where the parasitic mode is prohibited. The quality factor of the FBAR is enhanced by the introduction of the PnC. Indeed, the resonance and antiresonance frequencies passed from 1000 and 980 (without PnC) to 2350 and 1230 (with PnC), respectively. This is accompanied by a decrease in the electromechanical coupling coefficient from 10.60% to 6.61%.

scholarly journals The concept of thin film bulk acoustic resonators as selective CO<sub>2</sub> gas sensors

2017 ◽  
Vol 6 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Romy Hoffmann ◽  
Matthias Schreiter ◽  
Johannes Heitmann
Keyword(s):  
Thin Film ◽  
Microelectromechanical Systems ◽  
Gas Sensing ◽  
Acoustic Resonator ◽  
Acoustic Velocity ◽  
Indoor Environments ◽  
Acoustic Resonators ◽  
Film Bulk Acoustic Resonators ◽  
Film Bulk ◽  
Carbon Dioxide Co2

Abstract. Carbon dioxide (CO2) is a gas that well represents air quality in indoor environments as well as being an important greenhouse gas. However, the reliable and affordable sensing of environmental CO2 at room temperature, with techniques other than optical spectroscopy, remains an unsolved problem to this day. One major challenge for solid state sensors is the realisation of adequate selectivity, especially towards changing humidity. The thin film bulk acoustic resonator (FBAR) is a MEMS (Microelectromechanical systems) device that can not only detect gas-induced mass changes but also changes in the acoustic velocity and density of its layers. This multi-sensing provides a suitable platform for selective gas sensing. In this work we present studies done on polyaminosiloxane- and ethyl cellulose-functionalised FBARs regarding CO2 sensitivity, selectivity towards humidity, and stability. We demonstrate how CO2 and humidity signals can be separated and that CO2 can be sensed with a resolution of 50 ppm between 400 and 1000 ppm. Using the Mason model, we show how the acoustic velocity and density of an absorption layer can be determined and how changes in those parameters affect the resonance frequency shift. The understanding of these results ultimately presents a tool to theoretically separate any number of gas analytes.

Effect of c-axis tilted orientation ZnO thin film on shear-mode bulk acoustic resonator in liquid environment

2020 ◽  
Vol 10 (9) ◽  
pp. 1477-1483
Author(s):  
Ping Sun ◽  
Yurun Chen ◽  
Tingting Tang ◽  
Jian Shen ◽  
Xu Liu ◽  
...  
Keyword(s):  
Thin Film ◽  
Piezoelectric Materials ◽  
Longitudinal Mode ◽  
Acoustic Resonator ◽  
Shear Mode ◽  
Zno Thin Film ◽  
Liquid Environment ◽  
Acoustic Resonators ◽  
Film Bulk Acoustic Resonators ◽  
Film Bulk

ZnO has been widely used as piezoelectric materials in bulk acoustic resonators, especially in shear-mode film bulk acoustic resonators (FBAR). In this paper, we studied the effect of c-axis tilted ZnO thin film on shear mode FBAR in liquid environment. Mechanical impedances of FBARs are compared between shear-mode and longitudinal-mode wave due to their different orientations of ZnO thin film. It is found ZnO thin film with 43° c-axis tilted angels induces quasi-shear-mode acoustic wave only. The Q values of FBAR with 43° c-axis tilted ZnO are 256.94 in air at 0.8148 GHz, and 34.34 in water at 0.814 GHz, respectively. The shifts of the resonant frequencies are proportional to the square root of the product of viscosity and density of liquid medium, which is consistent with Kanazawa-Gordon theory and verified by actual experiment.

High Frequency Thin Film Acoustic Ferroelectric Resonators

2000 ◽  
Vol 655 ◽  
Author(s):  
Paul Kirby ◽  
Qing-Xin Su ◽  
Eiju Komuro ◽  
Masaaki Imura ◽  
Qi Zhang ◽  
...  
Keyword(s):  
Thin Film ◽  
Electromechanical Coupling ◽  
Acoustic Resonator ◽  
Electromechanical Coupling Coefficient ◽  
Coupling Coefficients ◽  
Pzt Thin Film ◽  
Film Bulk Acoustic Resonator ◽  
Film Bulk ◽  
Parasitic Components ◽  
Resonator Filters

AbstractBoth ZnO and PZT Thin Film Bulk Acoustic Resonator filters were fabricated, tested and modeled in this study. The development of an accurate Mason model allows the effect of particular parasitic components on the microwave s-parameters in the region of the series and parallel resonances to be identified. The parasitic components that limit the performance of our ZnO and PbZr0.3Ti0.7O3 Thin Film Bulk Acoustic Resonator filters are analysed. From an analysis of PbZr0.3Ti0.7O3 Thin Film Bulk Acoustic Resonator measurements values for the longitudinal acoustic velocity and electromechanical coupling coefficient can be derived. Measured PbZr0.3Ti0.7O3 Thin Film Bulk Acoustic Resonator filter responses confirm that the larger electromechanical coupling coefficients in this material compared to ZnO give wider filter band-widths.

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