Area-Selective Depositions of Self-assembled Monolayers on Patterned SiO2/Si Surfaces

Abstract

Area-selective depositions of SAMs have been demonstrated on SiO2/Si patterns, which are fabricated by synchrotron radiation (SR)-stimulated etching of SiO2 thin films on Si(100) substrates with SF6 + O2 as reaction gases and different types of masks. The SiO2 layer is made by thermal dry oxidation. A Co micro-pattern contact mask is fabricated by combining the photolithography and sputtering techniques, and a W submicron-pillar mask is deposited by using the focused ion beam-induced chemical vapor deposition (CVD). The SR-stimulated etching of SiO2 thin films on Si substrates is proven to have high spatial resolution, large selectivity, anisotropic etching, and low damage. The Co and W are found to be finer materials as SR etching masks. The etched patterns exhibit three-dimensional structures and the pattern surfaces are very flat and fit for depositing well-ordered monolayers on them. A dodecene SAM is deposited on the Si surface of the patterns, and trichlorosilane-derived SAMs (octadecyltrichlorosilane, and/or octenyltrichlorosilane) are deposited on the SiO2 of the patterns. The deposited SAMs are densely packed and well-ordered and are characterized by infrared spectroscopy, ellipsometry, and water contact angle measurements. Moreover, the surface of the octenyltrichlorosilane monolayer is changed from hydrophobic to hydrophilic by oxidizing the vinyl (–CH=CH2) end groups. This patterning of SAMs on SiO2/Si patterns will be a potential structure for fabricating novel silicon-based biosensors and in biomedical studies.