3D Monolithic Integration of ScAlN-based GHz MEMS Acoustic Filters on 200mm RFSOI Wafer

A wafer-level 3D monolithic integration of the scandium aluminum nitride (ScAlN) based radio frequency (RF) bulk acoustic wave (BAW) filters with RF silicon-on-insulator (RFSOI) switches were demonstrated for the first time, aiming for significant reduction of footprint and parasitics for the next generation RF frontend modules in wireless communication systems. The integrated switched filter operating at 2.5GHz achieves an insertions loss of <3.6 dB and bandwidth of >120 MHz within a compact area of <1mm
²
. The cross coupling between the BAW filter and RFSOI switch circuitry was investigated and a circuit model was developed to capture the interconnection parasitics introduced by the integration. Further characterizations, including high power intermodulation, temperature sweep and wafer-level uniformity test, were carried out to ascertain the robustness of the integration scheme.