Aqueous silane-surfactant co-dispersions for deposition of hydrophobic coatings onto pre-oxidized polysilicon

The application of hydrophobic coatings onto pre-oxidized polysilicon substrates is an effective method to prevent or reduce “release” as well as “in-use” stiction in microelectromechanical systems (MEMS). A chemical system consisting of a commercially available water dispersible silane (Siliclad®) has previously been shown to be useful in rendering polysilicon surfaces hydrophobic. In this paper, the improvement of the stability of such a chemical system is described. The objectives of the work reported in this paper are: (1) to characterize the stability of the organosilane in aqueous solutions under conditions suitable for the formation of hydrophobic coatings and (2) to investigate the influence of cationic surfactants on gelation rate of silane dispersions, on the adsorption of organosilane molecules onto pre-oxidized polysilicon and on the hydrophobic character of the coatings. Additionally, the effect of chain length and concentration for a series of alkyltrimethylammonium (C12,C14,C16) bromide surfactants on dispersion stability has been investigated.