Liquid and vapor phase silanes coating for the release of thin film MEMS

Stiction remains one of the biggest reliability problems in the fabrication of microelectromechanical systems (MEMS). This work investigates the techniques adapted to release thin-film devices (100 nm thick) and submicron gaps MEMS. First, a CMOS compatible wet release process was developed, using nonchlorinated silanes coating providing a high hydrophobicity (contact angle in the range of 110°). Second, a vapor phase release process based on the same chemistry is shown to be adequate to release thin-film beams from a silicon-on-insulator wafer, where the wet process failed. This is to the authors´ knowledge the first time that an in-use stiction-free release process has been demonstrated for such thin structures. The layers resist up to 300°C without damage and X-ray reflectivity confirmed that homogeneous monolayers were obtained.