Design and fabrication of a surface micromachined frequency tunable film bulk acoustic resonator with an extended electrostatic tuning range
IEEE International Ultrasonics Symposium, SEP 18-21, 2005, Rotterdam, NETHERLANDS
, p. 1840-1843
University of Antwerp
The frequency tuning of a surface micromachined film bulk acoustic resonator (FBAR), which integrates the tunable series capacitor and the piezoelectric resonating layer, had been demonstrated in previous publications. In the proposed structure, a movable piezoelectric cantilever is suspended above a bottom electrode. The air gap between the cantilever and the bottom electrode functions both as a tunable capacitor and an acoustic isolation. However, in case of electrostatic actuation, continuous tuning is limited in the range before the pull-in of the cantilever and is very small in prior art. In this paper, an improved design is suggested. By changing the the effective area ratio between the tunable capacitor and the piezoelectric resonating film, a larger continuous tuning range of 24.5MHz (0.39%) at a resonating frequncy of about 6.3GHz is realized.