Millimeter-wave MEMS capacitive switch in vacuum-sealed in-line wafer level package

In this paper, we present a millimeter-wave microelectromechanical systems (MEMS) switch with a microsecond switching time. The optimization of the mechanical structure, application of high actuation voltages and encapsulation with a vacuum-sealed package result in a higher speed with which a beam of the MEMS switch is pulled in and pulled out. In order to reduce the packaging cost, we encapsulate the MEMS switch using an in-line wafer level package (WLP) which is built during the same complementary metal-oxide semiconductor (CMOS) process in which the MEMS switch is built. The fabricated MEMS switch is a shunt circuit and capacitive contact type. The dimensions of the in-line WLP are 500 ¿m wide by 500 ¿m long. The measurement results show an insertion loss of 0.5 dB and an isolation of 15 dB at a frequency of 50 GHz. The measured switching time is 2.0 ¿s or less. This is the shortest switching time of a MEMS capacitive switch for millimeter wave applications as far as the authors know.