Integration of RF-MEMS, passives and CMOS-IC on silicon substrate by low temperature wafer to wafer bonding technique

In this paper, a novel platform technology for system level integration of RF-MEMS, RF passives and CMOS-IC on silicon substrate is reported. The RF passives and RF MEMS devices are fabricated on a low resistivity silicon wafer using Cu damascene process. After bonding the wafer to a CMOS wafer with recesses using benzocyclobutene (BCB) as intermediate layer and subsequently removal of bulk silicon, the RF passive components and RF MEMS devices are fully transferred onto CMOS wafer with silicon recesses underneath. The RF performance of RF-passive devices is improved significantly, e.g. the Q-factor of an inductor is improved by 174% and the resonant frequency is increased by 30%; the maximum available gain of a transformer is improved by 28%. RF-MEMS switch is sealed at wafer level and CMOS devices showed preserved device performance. This technology demonstrates the feasibility of building high performance, compact RF system on silicon substrate.