RF MEMS Shunt Capacitive Switches Using AlN Compared to Si3N4 Dielectric

RF microelectromechanical systems (MEMS) capacitive switches for two different dielectrics, aluminum nitride (AlN) and silicon nitride (Si3N4), are presented. The switches have been characterized and compared in terms of DC and RF performance (5-40 GHz). Switches based on AlN have higher down-state capacitance for similar dielectric thicknesses and provide better isolation and smaller insertion losses compared to Si3N4 switches. Experiments were carried out on RF MEMS switches with stiffening bars to prevent membrane deformation due to residual stress and with different spring and meander-type anchor designs. For a similar to 300-nm dielectric thickness, an air gap of 2.3 mu m and identical spring-type designs, the AlN switches systematically show an improvement in the isolation by more than-12 dB (-35.8 dB versus -23.7 dB) and a better insertion loss (-0.68 dB versus -0.90 dB) at 40 GHz compared to Si3N4. DC measurements show small leakage current densities for both dielectrics (