Modeling Tool for Capacitive RF MEMS Operating Bias Voltage Optimization

In this paper, dielectric charging process in dielectrics under bias voltage is investigated. Dielectric materials, used in numerous devices in microelectronics, can be subjected to significant electrical stress. These high electric fields impact the device lifetime. Actuation voltage measurements of capacitive RF MEMS as a function of stress time have been performed. Results show that the actuation voltage varies because of charge storage in the dielectric thin film. In this work a simulation code has been developed to model charge transport phenomena in insulators. This model takes into account tunnel and thermal effects in the dielectric and at the dielectric-metal interfaces. Thanks to this model, charge carrier distribution in the dielectric layer can be calculated. The actuation bias shift versus time, which can be responsible for RF capacitive structure failure, can also be determined. Experimental results can be reproduced thanks to simulations. This simulation tool is then used to define the optimal operating voltage value for a given RF MEMS device. It may also be used to assist in device design in microelectronics. Indeed for a given material set, the optimal operating voltage value is calculated as a function of device properties.