Novel compositions are provided for use in the vapor priming of substrates used in the preparation and production of microelectronic devices comprising a first component comprising an organosilane having a hydrolyzable silicon-nitrogen bond and a second component selected from the group consisting of a second organosilane different from the first component having a hydrolyzable silicon-nitrogen bond, a hydrocarbon, an ether, a disiloxane and an alkoxysilane in which all components have substantially the same boiling points at atmospheric pressure. These compositions which are vaporized and transported to an area of silylation on a substrate by an inert gas, silylate the substrate surface and provide for uniform successful coating with organic films. These organosilane mixtures allow for rapid vapor priming and silylation steps in the manufacture of microelectronic devices with successful subsequent coating of the substrates with uniform organic films.