Highly Textured (100)-Oriented and (111)-Oriented, Cobalt Mono Silicide Nanoribbons: Material Growth and Device Fabrication

Topological conductors with protected surface conduction states are candidates for scaling beyond copper interconnects. The topological semimetal CoSi is used here to study the properties of this class of materials because of the well-separated surface and bulk bands in its band structure. Highly textured CoSi nanoribbons were fabricated by sputtering Co on a hot Si (111) oriented facet. The as-grown CoSi nanoribbons showed a (100) surface orientation. A further annealing resulted in rearranging the CoSi surface orientation to (111). Devices for electrical testing of the nanoribbons were fabricated by patterning (100)-oriented silicon-on-insulator (SOI) into bars, then using TMAH etching for forming (111) sidewall facets on both edges of the SOI bars. A diluted HF (DHF) clean was used to strip the native oxide and H-passivate the Si (111) facets prior to cobalt deposition. The unreacted cobalt in the field region was selectively etched leaving isolated nanoribbons on the Si (111) facets. The nanoribbons were encapsulated by a dielectric and tungsten contacts to the nanoribbons completed the device fabrication. Initial electrical characteristics of nanoribbons with a width down to 20 nm and thickness of ~3 nm were measured.