Tungsten grid enhanced thin-film wafer-level encapsulation for monolithically integrated D-Band RF-MEMS switches in a 130 nm BiCMOS technology

In this study, a tungsten grid has been developed as enhanced encapsulation for monolithically integrated mm-wave RF-MEMS switches in the Back-End-Of-Line (BEOL) of a 130 nm SiGe BiCMOS technology of IHP. The applied thin-film wafer-level encapsulation has an impact on the RF-MEMS switch performance due to a parasitic silicon dioxide deposition on the suspended membrane inside the RF-MEMS cavity. This impact has been analyzed by optical profile measurements of the membrane bow. The thickness of parasitically deposited silicon dioxide has been minimized to about one tenth in comparison to the former developed encapsulation. The influence of the encapsulation process on the RF-MEMS switch performance has been minimized.