Sub-5 nm patterning <i>via </i>self-assembly and template-assisted assembly of colloidal nanocrystals

We explore using colloidal lithography and conventional fabrication tools for patterning substrates at and below the 5 nm scale. Our processing pathway combines bottom-up methods using inorganic nanocrystal (NC) synthesis and self-assembly techniques with top-down nanofabrication techniques. A pattern is established by the size, shape, and arrangement of discrete NC building-blocks, and the density is determined by the interparticle spacing of each element. The collective arrangement of each element sets the ensemble pattern, where each NC serves as a discrete hard etch mask. We explore self-assembly at a liquid-air interface and topographic template-assisted capillary assembly methods to establish the NC patterns. This pattern is transferred to the underlying substrate using inductively couple plasma reactive ion etching, and a selective chemical wet etch is used to remove any remaining mask material after pattern transfer. The NC systems explored are Fe₃O₄ spheres, TiO₂ rods, and GdF₃ rhombic plates with CF₄ and Cl₂ plasma etch chemistries. The goal of our pathway is to implement innovative processing methods into already well-established fabrication methods and technology, while maintaining process simplification and enabling wider access to patterning at the deep nanoscale.