Chemical vapour deposition of silanes

Chemical surface modification of oxide-covered surfaces by silanization is a well-known technique in such fields as gas and liquid chromatography, electro-chemistry and immobilization of biomolecules. In the commonly used silanization technique the silane is reacted with the surfaces in a liquid phase. If strict anhydrous conditions do not prevail, however, this technique often results in polymerization, irreproducibility and instability of the silane films. We report here on a gas phase silanization of silicon surfaces at elevated temperatures. The method comprises a washing and surface activation step followed by silanization at about 0.5–1 Nm^?2 and 80–190 °C depending on the type of silane. The silanized surfaces were characterized by ellipsometry, contact angle measurements and scanning electron microscopy, which revealed smooth, stable and reproducible silane films of monolayer character. A comparison of surfaces that were silanized in the gas phase with those that were silanized in the liquid phase was also made.