New method to evaluate materials outgassing used in MEMS thin film packaging technology

In this paper, a new method to characterize materials outgassing behavior is detailed. The understanding of these phenomena during all the process steps is required to improve vacuum thin film packaging. Starting from a standard hermetic fabrication process, each material of each layer is analyzed separately thanks to this innovative experimental method coupled with mass. Samples are sealed in an ampoule and a direct measure of pressure vs time and temperature is performed. From the variation of the pressure, the critical temperature (defined as the temperature for which pressure is above a given threshold) and the kinetics of the phenomenon are evaluated. The results are compared to thermodynamic simulations performed with the FactSage software. A full study of CVD deposited SiO2 is presented as an example. The results show all the potential of this experimental method and the improvements that have to be done to be able later onto choose best materials for thin film vacuum packaging.

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► A new method to analyze material outgassing is presented.
► From the experiment the ratio and nature of gases is detected.
► The knowledge of material outgassing properties is a key step for vacuum thin film packaging.