Investigation of area-dependent high-power failure of film bulk acoustic resonators

Film bulk acoustic resonators (FBARs) are widely used in radio frequency (RF) filters for wireless communication because of their high operating frequency and high quality factor. With the increase of high-power applications, ensuring device robustness has become a critical challenge. This study presents an investigation into the high-power failure behaviors and mechanisms of FBARs, specifically examining the role of active area, film thickness, and geometry. Experimental results demonstrate that small-area FBARs exhibit distinct failure characteristics compared to large-area devices. Small-area devices are governed by progressive spallation at electrode edges, which is induced by high-temperature oxidation and stress concentration, whereas large-area FBARs are prone to sudden structural fracture or short-circuiting caused by excessive thermal stress. Crucially, the study reveals a thickness-dependent transition in large-area devices, where short-circuiting and structural fracture correspond to distinct stress-severity regimes. Furthermore, dynamic evaluations demonstrate that these FBARs preserve strict electrical linearity right up to the point of catastrophic collapse. Based on these phenomenological findings, a thermo-mechanical coupling mechanism is proposed that goes beyond the conventional thermal-only model. Finally, we propose new design guidelines to enhance the power handling capability of FBAR devices.