Dense Organosilane Monolayer Resist That Directs Highly Selective Atomic Layer Deposition

Organosilane monolayers are part of many process flows in nanoelectronics and biotechnology because of their versatility. Monolayers that inhibit reactions on silicon/silicon oxide surfaces are needed to create patterns that direct the deposition of molecules and realize some of these applications. Organosilane monolayers on silicon oxide are typically deposited from the liquid phase by repeated deposition and cleaning cycles. Cleaning consists of solvent extraction, which removes weakly bound aggregates that physisorb in or on the layer during deposition. Adding a short immersion in an aqueous oxidizing base such as Standard Clean 1 (SC-1), which is a particle removal method in semiconductor manufacturing, reduced the time from 48 to 2 h to deposit an inhibiting monolayer. The SC-1 not only removed agglomerates but also re-hydroxylated the siloxane bridges at the interface between the monolayer and the silicon oxide surface based on X-ray photoelectron spectroscopy measurements of the hydroxyl group concentration. A line and space pattern in the organosilane monolayer made by conductive atomic force microscopy (C-AFM) was used to direct the precursors titanium tetrachloride (TiCl₄) and water vapor to deposit titanium dioxide (TiO₂) by atomic layer deposition (ALD) with a selectivity greater than 0.999. The titanium dioxide lines were about 170 nm wide, 9 nm high, and 20 μm long. The monolayer deposition procedure was done in a conventional laboratory using the common deposition solvent toluene and could be used to make versatile structures for nanodevice fabrication.