Impact of FBAR design on its sensitivity as in-liquid gravimetric sensor

• Published in: Sensors and actuators. A. Physical. Vol. 289; pp. 87 - 93
• Main Authors: Mirea, T., Olivares, J., Clement, M., Iborra, E.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.04.2019; Elsevier BV
• Subjects: Acoustic impedance; Acoustics; AlN-based thin film acoustic resonator; Chemical sensors; Crystal structure; Crystals; Density-viscosity; Dependence; Finite element analysis; Finite element method; Fluid dynamics; Gravimetry; Liquid; Microbalances; Organic chemistry; Quartz crystals; Resonant frequencies; Resonators; Sensitivity; Sensitivity analysis; Sensitivity enhancement; Sensors; Sound waves; Thin films; Viscosity; Liquid; Sensitivity; AlN-based thin film acoustic resonator; Density-viscosity
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2019.02.012

[Display omitted] •In-liquid sensitivity of shear SMRs can be boosted using specific designs.•This enhancement can be achieved without increasing the operating frequency.•Low impedance electrodes increase the sensitivity to density and viscosity.•Energy trapping effects at the sensing interface makes this possible.•The same effect occurs when applied as in liquid gravimetric sensors. In contrast to quartz crystal microbalances, the sensitivity of thin film bulk acoustic wave resonators (FBARs) is strongly dependent on all films comprising the multilayered structure. Previous studies proved that placing low acoustic impedance materials at the sensing surface of longitudinal-mode FBARs operating in air can enhance their mass sensitivity by modifying the energy trapped at the sensing surface. Here we investigate if the in-liquid sensitivity to density-viscosity and mass of shear-mode AlN-based solidly mounted resonators displays a similar dependence on the device configuration. By using the finite element simulation method accompanied by experimental verifications we demonstrate that for a given value of the resonant frequency, the sensitivity can be boosted by a proper design of the devices. The results can be of application to in-liquid physical sensors or to gravimetric chemical or biological sensors.