Nanometer-thin titania films with SAM-level stiction and superior wear resistance for reliable MEMS performance

Most MEMS devices involving contacting surfaces suffer from stiction and wear. While the development of self-assembled monolayer (SAM)-based processes has virtually eliminated stiction, wear remains a serious reliability issue. In this paper, the use of titania ultra-thin films as a means to reduce both stiction and wear is reported. Atomic layer deposition (ALD) is used for the film growth in order to ensure a uniform and conformal coating, effectively encapsulating the released polysilicon microelectromechanical systems (MEMS) devices. The application of 10-nm thin titania coating is shown to result in improved reliability of test microdevices. To further improve reliability, a vapor phase SAM coating is applied to TiO₂ encapsulated micromachines. Results on the tribological properties of both TiO₂-and SAM coated TiO₂-encapsulated microdevices are presented.