Monolithic fabrication of film bulk acoustic resonators above integrated circuit by adhesive-bonding-based film transfer

An integration process for the fabrication of thin film bulk acoustic wave resonator (FBAR) above the CMOS IC is proposed. An adhesive-bonding-based film transfer technique is utilized to transfer high resistivity Si film onto a CMOS chip. Benzocyclobutene (BCB) is used as an adhesive film. It is a heat resistive polymer and processes of temperature up to 300 °C are allowed on it. The CMOS is protected by BCB and thus is not damaged by plasma and chemical treatments. The transferred Si film offers flat and stable surface which is utilized for the deposition of ruthenium, aluminum nitride & aluminum to fabricate the FBAR structure. Finally, Si underneath the active device area is sacrificially etched to fabricate the air gap type FBAR. In this paper, we present the fabrication process and discuss important issues related to the fabrication.