Self-assembly patterning of epitaxial CoSi₂ wires

We have investigated a self-assembly process for patterning epitaxial CoSi₂ nanowires using local oxidation of silicides (LOCOSI). This involves single-crystalline, epitaxial CoSi₂ grown on Si(100) by molecular beam allotaxy (MBA). A mask consisting of 20 nm SiO₂ and 400 nm Si₃N₄, deposited by plasma enhanced chemical vapor deposition (PECVD) and patterned with conventional optical lithography, induces a stress field near its edges into the underlying CoSi₂/Si heterostructure. A rapid thermal oxidation step leads to the separation of the CoSi₂ layer in this region due to the concomitant anisotropic diffusion of the cobalt atoms in the stress field. Etching back the oxide underneath the nitride shifts the stress field underneath the mask leading to the formation of homogeneous silicide wires along the mask during a second oxidation step. Using this new approach, continuous wires with a minimum width of approximately 80 nm were observed.