Poly Silicon MEMS Technology Platform

The technology platform PSM-X2 features a low stress 10-30 µm thick poly silicon layer for the realisation of mechanical active and passive MEMS structures. The use of high resolution lithography allows minimal structure dimension down to 0.5µm.

An additional electrode layer beneath the active polysilicon layer is implemented. This gives the opportunity for out-of-plane signal detection or sensor stimulation. Additive functional layers enhance reliability and robustness of the MEMS devices (anti stiction, high-g shock).

For the wafer scale bonding of the sensor device and the protective encapsulation a dedicated multi pressure wafer level packaging process is applied using e.g. a gold silicon eutectic process at about 400°C. The metallic bond frame induces a hermetic encapsulation of the cavity and the pressure applied during the bond process will persist.

Integrated getter films allow cavity pressure levels down to 10-6 bar and a pressure ratio within adjacent cavities of up to 1:400. The application range of PSM-X2 platform includes e.g. inertial sensors, micro mirrors or electro-optic deflection devices.

Recently, Fraunhofer ISIT has developed an innovative process technology for the manufacturing of sophisticated MEMS scanners (²ε Process), called “Dual-Layer EpiPolySilicon Process”.

Following the success of the well established surface micromachining technology PSM-X2 for inertial sensors, the ²ε process is based on structuring two 30 microns thick epitactically grown polysilicon layers. This allows the realisation of staggered finger combdrives for mirror actuation and detection and the design of suspension