A pre-shaped wafer level packing strategy for RF MEMS

A pre-shaped wafer level packaging strategy for RF MEMS is presented. Silicon wafer is used as the capping chip for packaging of the Coplanar Waveguide (CPW) lines on the SCHOTT BOROFLOAT^® 33 glass substrate. The capping wafer is etched simultaneously from both sides which are carefully designed. One side is formed to on-chip cavities that will capsulate the RF MEMS devices; the other side is formed to complementary pattern so as to thin the unwanted part in advance, after bonding, this side will be etched through until the CPW pads are exposed. BCB (Benzo-Cyclo-Butene) is chosen for the seal and bonding material due to its excellent RF performance. The fabrication process is discussed in detail and the RF performance of the overall package is verified by 3D EM simulation software HFSS. The packaging structure keeps good RF performance up to 35GHz.