Investigation of dielectric degradation of microwave capacitive microswitches

This paper reports on the investigation of stiction and screening effects, which principally limit the lifetime of capacitive RF MEMS. These phenomena are the consequence of the dielectric charging which occurs during the running of the switch. To understand this effect, we have developed a specific test set which measures the microwave and electromechanic performances to evaluate the reliability of RF MEMS. Several experiments have thus been performed such as DC bias stress and cycling. These tests have shown that the dielectric charging creates a drift of the threshold voltages and that the difference between the pull-down and the pull-up voltages is an important parameter which drives the type of failure: stiction or screening.