Vacuum packaging processes integrating low temperature getter thin films – PRESTIGE

Single Crystal quartz is still currently the essential material for the development of high performance inertial MEMS sensors and time references, because of its piezoelectric properties and its good performance temperature stability. ONERA and RAKON, major actors in their respective domains, develop micro-sensors and time references aiming at the defence (navigation) and mobile phone markets. The operation principle of these structures is based on a mechanical resonator made of single quartz package in vacuum to improve its performances. Naturally, the performances of the packaged structures is highly dependent on the long term stability of the vacuum inside the package.

These applicative markets are currently turning towards the 3D integration of small size structure (typically <1 cm3). To answer these new needs, ONERA and RAKON are in the urge of reducing the volume of their current solutions by working on the packaging technique. A reduction of 4 fold of the packaged volume is seeked.

An important development has already been done on the packaging of silicon-based structures. The originality of the work proposed in this project is the following :
- The used substrate is single quartz, which implies the development of low température processes (<300°C) in ordre to preserve the piezoelectric properties of the material and the quality of the metallic contacts (important for piezo actuation and détection).
- The package volume and the base pressure (10-3 mbar) imply a very low leak rate compared to the state of the art (about 10-15 atm.cm3/s) in order to maintain the vacuum level during several years.
- Therefore, adapted measurement techniques need to be set up to allow such a measurement

Finally, getter materials associating low température activation (<300 °C) and high performance need to be developed and packaged.
FOGALE NANOTECH has been developing for 10 years measurement solutions dedicated to the characterization of micro-resonators. Emanating from several industrial partners, the urging demand for control setups dedicated to the characterization of packaged structures motivâtes FOGALE to take place in this collaborative project.

In this project, we propose to develop packaging processes compatible with the intégration of high performance, quartz based MEMS resonators (ONERA) and BAW time references (RAKON), with the following performances : low température (<300 °C), low residual pressure (<10-3 mbar), low leak rate (<10E-16 atm.cm3/s). In order to ensure the industrial transfer of the packaging processes developed in this project, a part of these processes will be transferred to RAKON in the framework of this project. Moreover, the characterization means set up by FOGALE will give rise to a commercial product dediacted to control lines.

The consortium ONERA / Université Paris Sud (IEF) / FOGALE / RAKON gathers four entities identified as major actors in their specific domain of expertise. The PRESTIGE project will gather all the necessary know-how, from realizations and material development on quartz material to the characterization techniques dans industrial transfer.