Determination the Effects of Structural Parameters on Pull Down Voltage of RF MEMS Switches

In this paper, the sensitivity of pull down voltage of RF MEMS switches are investigated. Inspections are done with respect to the Young modulus, biaxial residual stress, Poisson's ratio, bridge width, bridge thickness, bridge length and CPW center conductor width. In this regard, sets of orthogonal experiments are designed based on the Latin Cubes concept. Then the results of the experiments (i.e. pull down voltage) are interpolated on a response surface. The response surface shows the self and the mutual effects of the factors on the level of the pull down voltage. It is seen that the minor changes of the structural parameters has major effect in the level of the pull down voltage. Consequently, after RF MEMS design process, sensitivity analysis must be done with respect to the structural parameters. The level of pull down voltage can be reduced by small changes in the structural parameters. It is seen that the response surface can be readily used for analysis of the effects of parameters and with the small amounts of experiments, suitable results are achievable on the level of the pull down voltage. Detailed analysis shows that the Young modulus, biaxial residual stress, bridge thickness, bridge length and the gap between the switch and actuation electrode are increasing self effect, while the other parameters effects are decreasing self effects. The maximum and minimum self effects are the effects of the gap between the switch and actuation electrode and bridge width, respectively. Mutual effects investigations shows that the gap between the switch and actuation electrode and biaxial residual stress mutual effect is the largest decreasing effect, while the gap between the switch and actuation electrode and bridge thickness mutual effect is the largest increasing effects.