Mass sensitivity of multilayer thin film resonant BAW sensors

“…In FBAR however the electrodes will take up a larger portion of the acoustic path and can result in the case of low acoustic impedance material in sensitivity amplification (Wingqvist et al 2008), but still the Sauerbrey expression can serve as a quite fair estimate of the order of magnitude of sensitivity.…”

Section: Addition/removal Of Materialsmentioning

confidence: 99%

Thin-film electro-acoustic sensors based on AlN and its alloys: possibilities and limitations

Wingqvist

2012

Microsyst Technol

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Sputter deposited aluminum nitride (AlN) thin films have played a central role for the successful development of the thin film electro-acoustic technology. The development has been primarily driven by one device-the thin film bulk acoustic resonator, with its primary use for high frequency filter applications for the telecom industry. Recently, increased piezoelectric properties in AlN through the alloying with scandium nitride have been identified both experimentally and theoretically. This opens up new possibilities for the thin film electro-acoustic technology.Here expectations and discussions are presented on acoustic FBAR sensor performance when based on AlN as well as on such AlN alloys to identify possible benefits and limitations. Inhere, the distinction is made between direct and in-direct (acoustic) use of the piezoelectric effect for sensor applications. These two approaches are described and compared in view of their advantages and possibilities. Especially, the indirect (or acoustic) use is identified as interesting for its versatility and good exploitation of the thin film technology to obtain highly sensitive sensor transducers. It is pointed out that the indirect approach can well be obtained internally in the piezoelectric material structure. Original calculations are presented to support the discussion.

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“…Effectively, thin film electroacoustic technology has made possible to fabricate quasi-shear mode thin film bulk acoustic resonators (FBAR), operating with a sufficient electromechanical coupling for use in liquid media at 1-2 GHz (Bjurstrom et al, 2006;Gabl et al, 2004); however, the higher frequency and the smaller size of the resonator result in that the boundary conditions have a much stronger effect on the FBAR performance than on the QCM response. This will result in a higher mass sensitivity, but in an increased noise level as well, thus moderating the gain in resolution (Wingqvist , 2008. So far only publications of network analyzer based FBAR sensor measurements have been published in the literature, which show that the FBAR mass resolution is very similar if not better than for oscillator based QCM sensors (Weber et al, 2006;Wingqvist , 2008Wingqvist , 2009).…”

Section: Fbar Devices For Biosensing Applicationsmentioning

confidence: 99%

“…This will result in a higher mass sensitivity, but in an increased noise level as well, thus moderating the gain in resolution (Wingqvist , 2008. So far only publications of network analyzer based FBAR sensor measurements have been published in the literature, which show that the FBAR mass resolution is very similar if not better than for oscillator based QCM sensors (Weber et al, 2006;Wingqvist , 2008Wingqvist , 2009). The first shear mode FBAR biosensor system working in liquid environment was reported in 2006 (Weber et al, 2006).…”

Section: Fbar Devices For Biosensing Applicationsmentioning

confidence: 99%