Thin-film bulk acoustic resonator

A thin-film bulk acoustic resonator (FBAR or TFBAR) is a device consisting of a piezoelectric material manufactured by thin film methods between two conductive – typically metallic – electrodes and acoustically isolated from the surrounding medium. The operation is based on the piezoelectricity of the piezolayer between the electrodes.

Basic FBAR structure

FBAR devices using piezoelectric films with thicknesses typically ranging from several micrometres down to tenths of micrometres resonate in the frequency range of 100 MHz to 20 GHz.[1][2] FBAR or TFBAR resonators fall in the category of bulk acoustic resonators (BAW) and piezoelectric resonators and they are used in applications where high frequency, small size like thickness and/or weight is needed.

Industrial application areas of thin film bulk acoustic resonators are ranging from high frequency signal filtering specifically for mobile telecommunication devices, crystal replacements, energy harvesting, acoustic speakers in systems where size matters like hearings aids, as part of mechanical qubits and to sensory.[3][4][5][6]

  1. ^ Lakin, K.M.; Wang, J.S. (1981). "Acoustic Bulk Wave Composite Resonators". Applied Physics Letters. 38 (3): 125–127. Bibcode:1981ApPhL..38..125L. doi:10.1063/1.92298.
  2. ^ Lakin, K. (2003). "A review of thin-film resonator technology". IEEE Microwave Magazine. 4 (4): 61–67. doi:10.1109/MMW.2003.1266067.
  3. ^ "Intensifying Technology Competition in the Acoustic Wave Filter Market".
  4. ^ Joshi, Sanjog Vilas; Sadeghpour, Sina; Kraft, Michael (June 2023). "Low-cost piezo-MEMS speaker technology". Micro and Nano Engineering. 19. doi:10.1016/j.mne.2023.100213.
  5. ^ Zhang, Yi; Luo, Jikui; Flewitt, Andrew J.; Cai, Zhiqiang; Zhao, Xiubo (30 September 2018). "Film bulk acoustic resonators (FBARs) as biosensors: A review". Biosensors and Bioelectronics. 116: 1–15. doi:10.1016/j.bios.2018.05.028. PMID 29852471.
  6. ^ Yang, Yu; Kladarić, Igor; Drimmer, Maxwell; von Lüpke, Uwe; Lenterman, Daan; Bus, Joost; Marti, Stefano; Fadel, Matteo; Chu, Yiwen (2024). "A mechanical qubit". Science. 386 (6723): 783–788. doi:10.1126/science.adr2464. PMID 39541455.