Abstract:
The sensitivity of many microelectromechanical systems (MEMS), such as resonant sensors or thermal devices, is degraded if they are not operated in a rarefied atmosphere. To optimize their performance and limit viscoelastic or conductive losses, these microdevices are placed in vacuum packaging for their entire life (minimum 10 years).
Two predominant sources of gas must then be controlled: outgassing from the inner surface of the cavity during the bonding, and leakage through the sealing. A technological solution for achieving good vacuum quality throughout the lifetime of the MEMS is the use of getter materials.
This thesis investigates a new family of yttrium-based getter materials, in particular the Y-Ti alloy, for vacuum packaging of MEMS, with the aim of achieving an activation temperature below 300°C and high sorption capacity for gases trapped in the cavity, especially hydrogen.
In order to study the microstructure, activation temperature and sorption capacity of these materials, thin layers of yttrium-based getter films were analyzed using a variety of experimental methods: electrical measurements, electron microscopy, DRX and ion beam analysis (RBS, NRA, ERDA). The results show that
yttrium is particularly reactive at ambient temperature. Alloying it with titanium makes it less reactive, reduces its activation temperature and also improves its sorption capabilities.