MEMS Varactor with High RF Power Handling Capability for Tuning of Wideband Low Noise RF VCOs

High Power handling capabilities are not the main focus in MEMS varactor research and development. In this paper MEMS varactors with excellent RF power handling capabilities of up to 16 V-PP for application in low noise wideband RF VCOs (Voltage controlled oscillators) have been designed, fabricated and characterized. These MEMS varactors are embedded in the BEOL (Back end of line) metallization stack of a state- of-the-art Si/SiGe BiCMOS semiconductor process and show an overall capacity ratio of > 4:1. The pseudo linear tuning range before the membrane snap-down is 1.4:1 without and 1.65 after de-embedding of interconnect and substrate parasitics. This tuning range is not reduced significantly even when applying RF amplitudes of up to 16 V-PP. This high power handling capability makes this type of MEMS varactor an excellent candidate for tuning of wideband ultra-low noise RF VCOs. The mechanical and RF design was carried out applying a novel interactive approach that allows an in depth understanding of the various design constrains.