Outgassing characterization of MEMS thin film packaging materials

In the field of MEMS packaging technology the pressure limit inside the cavity is a crucial parameter. As the cavity size becomes smaller and smaller the vacuum is mainly affected by the outgassing of the materials used in the fabrication process. A full characterization of this phenomenon for oxides that can be integrated as encapsulation layer is presented in this study. A combination of dynamic outgassing, Residual Gas Analysis (RGA) and thermodynamic simulations is involved to fully investigate the material outgassing behavior. The temperature and the nature of released gases are evaluated indicating the optimal annealing or other cleaning process before the sealing of cavities. Moreover the combination of these oxides with a getter material is analyzed. The affinity between carbon dioxide, nitrogen, hydrogen and the getter material is demonstrated as well as its non-reactivity with hydrocarbons. The pressure inside the cavity can be efficiently decreased by integrating this pumping material. Therefore a selection of materials and new fabrication processes can be considered using those results.