Film bulk acoustic resonator pressure sensor with self temperature reference

• Published in: Journal of micromechanics and microengineering Vol. 22; no. 12; pp. 125005 - 6
• Main Authors: He, X L, Garcia-Gancedo, L, Jin, P C, Zhou, J, Wang, W B, Dong, S R, Luo, J K, Flewitt, A J, Milne, W I
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.12.2012; Institute of Physics
• Subjects: Acoustics; Exact sciences and technology; FBAR; Frequency shift; General equipment and techniques; Holes; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Micromechanics; Packages; Physics; pressure sensor; Pressure sensors; Resonators; sealed cavity; Sensors; temperature sensor; Transducers; Pressure sensors; Temperature sensors; Frequency shift; Trench technology; Resonance frequency; Vibrational modes; Zinc oxide; System on a chip; Acoustic resonators; Piezoelectric semiconductors
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/22/12/125005

A novel film bulk acoustic resonator (FBAR) with two resonant frequencies which have opposite reactions to temperature changes has been designed. The two resonant modes respond differently to changes in temperature and pressure, with the frequency shift being linearly correlated with temperature and pressure changes. By utilizing the FBAR's sealed back trench as a cavity, an on-chip single FBAR sensor suitable for measuring pressure and temperature simultaneously is proposed and demonstrated. The experimental results show that the pressure coefficient of frequency for the lower frequency peak of the FBAR sensors is approximately −17.4 ppm kPa−1, while that for the second peak is approximately −6.1 ppm kPa−1, both of them being much more sensitive than other existing pressure sensors. This dual mode on-chip pressure sensor is simple in structure and operation, can be fabricated at very low cost, and yet requires no specific package, therefore has great potential for applications.