A TSV-packaged SP6T RF MEMS switch with ultra-thin profile and suppressed substrate loss for DC to Ku band application

The evolution of wireless communication imposes stringent requirements on RF front-end modules, specifically demanding switches with ultra-thin profiles and wideband coverage up to Ku band. However, conventional packaged MEMS switches often result in excessive device height, creating a bottleneck for compact system integration. To address these challenges, this study presents a TSV-packaged Single Pole Six Throw (SP6T) RF MEMS switch that simultaneously achieves an ultra-thin profile and superior signal integrity. The device features a total height of only 300 μm, achieved through a substrate grinding process. To compensate for the impedance variations induced by the ultra-thin substrate and air cavity, two types of Heterotypic Microstrip (HMS) transmission lines are proposed and optimized for signal matching from DC to Ku band. The switches are fabricated using a combination of surface and bulk micromachining, including gold-alloy electroplating, Au-Sn bonding, and TSV processes. Measurement results verify the design strategy: the switch with a 300-μm height exhibits significantly improved insertion loss (IL) suppression compared to thicker counterparts. The best IL reaches 2.0 dB at 18 GHz, with return loss better than 14 dB and isolation exceeding 18 dB across the DC ~18 GHz band. Furthermore, mechanical and thermal simulations confirm that the substrate thinning does not compromise contact force or heat dissipation. These results demonstrate that the proposed packaging scheme successfully solves the conflict between miniaturization and high-frequency performance, offering a promising solution for next-generation mobile RF systems.