Integration of RF MEMS and CMOS IC on a Printed Circuit Board for a Compact RF System Application Based on Wafer Transfer

In this paper, a novel platform technology for integrating radio-frequency microelectromechanical systems (RF-MEMS) and CMOS on a printed circuit board (PCB) is demonstrated. An RF-MEMS switch is constructed on top of a CMOS IC wafer. The stacked structure is subsequently transferred onto a PCB substrate (i.e., FR-4) by thermal compressive bonding, mechanical grinding, and wet removal of bulk silicon. The measurement of the fabricated RF-MEMS switch on the FR-4 substrate shows promising results. It has an insertion loss of 0.25 dB at 20 GHz and an isolation of 25 dB at 20 GHz. At the same time, the performance of CMOS is not degraded during the integration process; the drain current in the p-MOS transistor remained unchanged, whereas that in the n-MOS transistor showed a slight improvement after transfer. This technology is very useful for compact RF system on PCB material with low power consumption and high performance for wearable, wireless, and implantable device applications.