Until now, the determination of the hermeticity of microelectronic packages is related to the MIL-STD-883 method 1014
which is based on the He leak detection method. But this method is no more suited for small packages due to the
resolution limit of the apparatus used conventionally. Indeed the minimum detectable leak rate is of the order of 5.10<sup>-11</sup>
atm.cm<sup>3</sup>.s<sup>-1</sup>. Leaks induced by non hermetic MEMS packages are often one order of magnitude smaller. So, the
sensitivity of the He leak detector method is too low and this method can not be applied anymore. The MEMS packages
produced with wafer level encapsulation techniques, require new methodologies to measure hermeticity appropriately
and accurately. The purpose of this paper is to present the development of alternative methods for testing the hermeticity
of MEMS micro-cavities. Two methods will be investigated in the context of this study: The membrane deflection
measurement exposed to different pressures, using optical profilometry, and the measurement of the variation of gas
concentration in a sealed silicon cavity by Fourier-transform infrared spectroscopy (FT-IR). The calculated leak rates are
compared for samples where standard fine leak test gave no results. The values obtained for the leak rates within optical
test and FT-IR test for the same sample are identical, showing the relevance of these two methods.
This paper presents hermeticity tests carried out on organically sealed MEMS micro-packages, using Fourier Transform Infra Red (FTIR) spectroscopy. Infrared spectroscopy, classically dedicated to material analysis, can be used to monitor the internal pressure of micro-packages, and to assess so their hermeticity. This technique was applied to BCB sealed micro-packages to study the influence of different parameters on their hermeticity properties, like the sealing ring dimensions or the addition of an external coating. The technique was validated for silicon micro-packages with a volume of 5 mm<sup>3</sup> or more. Moreover, measurements carried out on micro-cavities with external parylene coatings have demonstrated that infrared spectroscopy measurements could be performed on MEMS packages with hermetic organic coatings.