Dielectric material impact on capacitive RF MEMS reliability

The influence of different types of dielectrics on the switching behaviour and reliability of capacitive RF MEMS switches fabricated by metal surface-micromachining is investigated. Sputtered AlN layers are compared to PECVD Si3N4 and Ta2O5 layers. It has been found that switches with sputtered AlN can be operated without failure in a wide range of driving conditions. Besides the dielectric charging problem another degradation has been observed independent of the dielectric material. The effect only occurs for operation in ambient air and is probably caused by an electrochemical reaction.