IMPACT OF BIASING SCHEME AND ENVIRONMENT CONDITIONS ON THE LIFETIME OF RF-MEMS CAPACITIVE SWITCHES
P. CZARNECKI, X. ROTTENBERG, R. PUERS, I. DE WOLF

Abstract. This paper presents a study of the lifetime of capacitive RF-MEMS switches actuated in air, nitrogen and helium atmospheres with unipolar and bipolar actuation. The switches failed by stiction attributed to the charging of the dielectric layer used in the electrostatic actuation areas. Our measurement data show that both environment conditions and biasing schemes have a clear impact on the lifetime of the devices, these parameters do not change the failure mechanism of the devices. The bipolar actuation improves the lifetime of the switches because the total trapped charge over a complete actuation cycle is close to nil. Nevertheless, we show that the variance of the trapped charge distribution is not nil and can still lead to the failure of the devices by its stiction or by the drift of its up-state capacitance. Finally, the data gathered in this study show a clear relation between the electric strength of the environment medium and the lifetime of the devices. The higher the electric strength of the atmosphere is, the higher the lifetime of the device is. This indicates that the breakdown of the small gaps between the moving electrode and the dielectric layer might play an important role in the dielectric charging and as a consequence in the lifetime of RF-MEMS capacitive switches. Further tests are ongoing to verify the agreement of the measurements with Paschen’s law.