DocumentCode :
1129937
Title :
Micromachined Acoustic Resonant Mass Sensor
Author :
Zhang, Hao ; Kim, Eun Sok
Author_Institution :
Dept. of Electr. Eng.-Electrophys., Univ. of Southern California, Los Angeles, CA, USA
Volume :
14
Issue :
4
fYear :
2005
Firstpage :
699
Lastpage :
706
Abstract :
This paper describes a highly sensitive, film bulk acoustic resonator (FBAR) mass sensor (built on a micromachined silicon-nitride diaphragm with a piezoelectric thin film and Al electrodes) that can operate in vapor and liquid. The sensitivity of the device to mass change on its surface has been investigated by having various thicknesses of silicon-nitride support layer and also of Al layer. The sensor is measured to have a mass sensitivity of 726 cm ^2 /g, which is about 50 times that of a typical quartz crystal microbalance (QCM). In vapor, the sensor (operating at around 1 GHz and having a relatively high quality (Q) factor of 200–300) shows a minimum detectable frequency shift of about 400 Hz, which corresponds to a mass change of 10^-9 g/cm ^2 on the sensor surface, comparable with that detectable by a QCM. In liquid, though the Q usually drops more than an order of magnitude, we obtain a Q of 40 at 2 GHz by using a second harmonic resonance of the resonator. And with the Q, a minimum 5 ppm resonant frequency shift can be detected, which corresponds to 10^- 8 g/cm ^2 change on the sensor surface. \\hfill \\hbox {[1374]}
Keywords :
acoustic resonators; bulk acoustic wave devices; mass measurement; microbalances; micromachining; surface acoustic wave sensors; acoustic resonant mass sensor; film bulk acoustic resonator; micromachined silicon-nitride diaphragm; piezoelectric thin film; quartz crystal microbalance; Acoustic sensors; Acoustic signal detection; Acoustic waves; Biosensors; Chemical and biological sensors; Film bulk acoustic resonators; Frequency; Piezoelectric films; Resonance; Surface acoustic waves; Acoustic resonator; film bulk acoustic resonator (FBAR); mass sensor; microbalance; quartz crystal microbalance (QCM);
fLanguage :
English
Journal_Title :
Microelectromechanical Systems, Journal of
Publisher :
ieee
ISSN :
1057-7157
Type :
jour
DOI :
10.1109/JMEMS.2005.845405
Filename :
1492421
Link To Document :
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