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The objective of this research has been to develop the chemistry and techniques for the application of hydrophobic coatings on polysilicon substrates from aqueous media with the ultimate goal of applying these techniques for preventing or reducing release as well as in use stiction in microelectromechanical structure devices. In this paper, the results obtained from a chemical system consisting of a water dispersible silane and a cationic surfactant are presented. Key experimental variables that have been investigated are the concentration of reactive silane and cationic surfactant, type of oxidation pretreatment, pH of the silane dispersion, and curing temperature.

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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 (C 12 ,C 14 ,C 16 ) bromide surfactants on dispersion stability has been investigated.

Buffered hydrofluoric acid (BHF) solutions containing HF and NH4F are widely used in the manufacturing of silicon-based integrated circuits. The adsorption/desorption characteristics of a commercially available, high purity, polyglycidol type surfactant (OHS) onto/from silicon from buffered hydrofluoric acid (BHF) solutions was studied by in situ attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). The challenge in these measurements was to resolve the C-H peaks, in the 2800-3000 cm -1 region of the surfactant spectrum, that were masked by the strong absorbance due to N-H caused by a large amount of NH4 + ions in the solution. A technique has been developed to overcome this limitation. The principle of this technique is to carry out the surfactant adsorption in BHF solutions followed by the replacement of NH4 + ions by alkali-metal cations, such as K + and Cs + , to allow better resolution of the C-H peaks from the baseline. Extrapolation of the adsorption density to time zero yields the adsorption density in the presence of NH4 + . Using this technique, the adsorption density of OHS surfactant in a buffered HF solution containing 7 parts of NH4F (40%) and 1 part of HF (49%) was found to be approximately 20% higher than that in dilute HF solutions.