Contact Modeling of DC Contact RF MEMS for Investigation of the Microcontact Degradation Mechanism
Résumé
RF MEMS devices have already demonstrated very attractive performances to introduce some intelligence in the front end architectures. The insertion of RF MEMS into real architecture will necessitate reduced actuation voltage, dimensions and a better control of the electrical and electromechanical behavior that will give more importance to surface effects and their understanding and modeling. So far, surface effects were ignored in the analysis, because of the difficulty to generate a rough surface model and also to simplify the model in order to reduced computation times. With the increase of computation capabilities, the topography of the surface can be included in finite element simulations if appropriate simulation methodology is implemented. In order to give an explanation to the microcontact degradation phenomenon, gold DC contact switches are tested on an experimental set up in NOVAMEMS that allows the switch ageing under controlled atmosphere and makes possible the analysis of contact behavior with cycling. A correlation is established between the electromechanical characterizations and finite element simulations. From the surface characterization, we generate the real shape of both rough surfaces that come into contact and to predict the real contact area and size of each contact spots. The obtained results show actually an increase in contact resistance with cycling. However, the variation isn't as large as the experimental measurements. Other failure phenomena have to be taken into account such as organic deposits, contamination or hardening to complete the analysis.