Design and fabrication of a miniaturized bulk acoustic filter by high aspect ratio etching

Abstract

A 2.45-GHz filter is fabricated by thin film bulk acoustic wave resonator (FBAR) technology. It is designed to minimize die size and simplify the fabrication process simultaneously by using inductive coupling plasma etching. The quality factor of a fabricated single resonator is 1567 and the electromechanical coupling coefficient is 5.7%. The fabricated filter has minimum insertion loss around 1.5 dB and maximum insertion loss at 3.6 dB in 83.5-MHz bandwidth, which is suitable for WLAN and Bluetooth applications. © 2005 Society of Photo-Optical Instrumentation Engineers.