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

Parvais, Bertrand [UCL] Pallandre, A. Jonas, Alain M. [UCL] Raskin, Jean-Pierre [UCL]

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 degrees). 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 degrees C without damage and X-ray reflectivity confirmed that homogeneous monolayers; were obtained.