FABRICATION OF MICROMECHANICAL SWITCHES FOR ROUTING RADIO-FREQUENCY SIGNALS

Micromechanical switches have several advantages over other switch tec hnologies for the routing of microwave and mm-wave signals. They offer low loss, low switching power, very low standby power, and are extrem ely linear. The switching speeds are very slow compared to solid state switches; however, for a number of applications, their specifications appear attractive. For instance, electronically steerable antenna arr ays operating at 10, 20, and 30 GHz need phase shifters for each anten na element. Micromechanical RF switches that offered lower losses coul d find significant applications as phase shifters for telecommunicatio ns applications. We describe the fabrication of membrane micromechanic al RF switches that switch signals of 10 GHz and higher. Dry etching p lays a critical role in fabrication. in particular the isotropic remov al of a sacrificial polymer layer between the bottom electrode and the membrane is a critical process. Reasonable rates must be obtained at moderate temperatures and there must be as little residue as possible. A high degree of selectivity over that of the capacitor dielectric is also a requirement. Our process should be compatible with microwave m onolithic integrated circuit (MMIC) processing technology allowing int egration with RF amplifiers and other components. (C) 1996 American Va cuum Society.