Silicon substrates, surface functionalization silanization

Comyn [1] has pointed out that maximum bond strength and consequently greater adhesion between the substrate and polymer could be achieved with a monolayer of silane bound to both the adherend and adhesive. The current investigation was undertaken to evaluate the possibility of monolayer level depositions on silicon substrates by employing a few w -functionalized alkanoyl-substituted derivatives of APTES which will provide polar moieties as well. The interactions of these functionalized silanes covalently immobilized on silicon with octadecylamine and octadecanoic acid, used as models for basic and acidic polymeric adhesives, were also examined in this study. Characterization of the silanized surfaces as well as studies on their interactions with the above two chemical probes were carried out through ellipsometric and XPS measurements. 

Primers for adhesive bonding chemically functionalize the substrate surface to provide pathways for chemical bonding with a selected silicone cure system. The increase of chemical bond improves adhesion durability. The main disadvantage of priming the substrate is the addition of an extra step in the whole process of adhesive application. The primers are usually Silane adhesion promoters, a reactive alkoxy silane molecule, oligomer, or a mixture of two or more different silanes. 

Based on this approach Schouten et al. [254] attached a silane-functionalized styrene derivative (4-trichlorosilylstyrene) on colloidal silica as well as on flat glass substrates and silicon wafers and added a five-fold excess BuLi to create the active surface sites for LASIP in toluene as the solvent. With THF as the reaction medium, the BuLi was found to react not only with the vinyl groups of the styrene derivative but also with the siloxane groups of the substrate. It was found that even under optimized reaction conditions, LASIP from silica and especially from flat surfaces could not be performed in a reproducible manner. Free silanol groups at the surface as well as the ever-present impurities adsorbed on silica, impaired the anionic polymerization. However, living anionic polymerization behavior was found and the polymer load increased linearly with the polymerization time. Polystyrene homopolymer brushes as well as block copolymers of poly(styrene-f)lock-MMA) and poly(styrene-block-isoprene) could be prepared. 

Other classes of silanes, namely alkoxy, halogenated, and other silanes [3, 9], are known to react with —OH containing compounds, and, therefore, should also function as adhesion promoters or surface modifiers for —OH containing substrates. Texas Instruments, for example, employed a 2% xylene solution of phenyltrichlorosilane to provide resist image adhesion to various oxide wafer substrates [10]. References 3, 9, and 10 describe many of these materials applied to silicone dioxide substrates. As for HMDS treatment, ESCA evidence of reactions to verify covalent bonding to surface silanol groups will be provided in... 

---