RF-MEMS packaging by using quartz caps and epoxy polymers

This work reports on RF MEMS chip capping to protect sensitive devices by quartz caps having a cavity to enclose MEMS devices and an epoxy film polymer as a sealing ring. Full hermeticity is not possible due to the permeability of polymer but the goal to protect the mobile parts of the devices during dicing and assembling was achieved. Good RF MEMS devices are produced by die-to-die bonding and a reliable fabrication process is defined while wafer-to-wafer process still needs improvement to increase the fabrication yield. In this paper the fabrication process for both die-to-die and wafer-to-wafer 0-level capping is presented. Good adhesion of caps to the substrate is demonstrated by shear tests, while RF measurements on CPW lines indicate a negligible insertion loss increase. Capping of both capacitive and ohmic contact switches is reported showing no loss of functionality but a modification of actuation voltage induced by thermal treatment.