Effect of temperature on in-use stiction of cantilever beams coated with perfluorinated alkysiloxane monolayers

The effect of annealing (for temperatures up to 300 degC) on the antistiction performance of perfluorinated self-assembled monolayers (SAMs) is characterized using polycrystalline Si cantilever beam arrays. The monolayers 1H,1H,2H,2H, perfluorodecyltrichlorosilane (FDTS) and 1H,1H,2H,2H, perfluorodecyldimethylchlorosilane (FDDMCS) deposited from both liquid and vapor phase are investigated. It is observed that stiction decreases upon annealing for both monolayers and for both types of deposition. FDTS, however, displays greater temperature stability than FDDMCS regardless of the mode of deposition. The higher thermal resistance of the FDTS underscores the importance of monolayer crosslinking since unlike FDDMCS, FDTS forms a siloxane network on the surface. Further vacuum annealing and X-ray photoelectron spectroscopy experiments are performed to identify chemical changes in the monolayer during annealing. Incipient monolayer degradation is observed, with loss of the whole fluorinated monolayer chain. This process appears drastically different from the decomposition mechanism of hydrogenated alkylsiloxane monolayers such as octadecyltrichlorosilane (OTS)