Air-gap type film bulk acoustic resonator using flexible thin substrate

This paper addresses the utilization of an ultra thin silicon wafer with thickness of 50 μm to fabricate film bulk wave acoustic resonator (FBAR) generating resonant motion at 2.5 GHz which can be applied to more flexible and accumulated microsystems. As the information and communication technology starts to improve, smaller and lighter systems are needed to be flexible in a worldwide market. To accomplish this many ideas on making the heavy and rigid pieces, such as RF filter or duplexer, thin FBAR using microelectromechanical systems technology is presented in this paper. As we fabricate the FBAR using thin silicon wafer with thickness of 50 μm, it is possible to realize integrated flexible microsystems and acquire properties better than the existing devices. The resonance characteristics of thin FBAR are predicted through MATLAB simulation and then thickness of electrode and piezoelectric thin film optimized are acquired. A parallel resonance frequency is measured at 2.487 GHz. The insertion loss, Q-factor, and Keff2 are also 1.368 dB, 996.68, and 3.91%, respectively.