Fabrication of sub-10nm metallic lines of low line-width roughness by hydrogen reduction of patterned metal-organic materials

The fabrication of very narrow metal lines by the lift-off technique, especially below sub-10nm, is challenging due to thinner resist requirements in order to achieve the lithographic resolution. At such small length scales, when the grain size becomes comparable with the line-width, the built-in stress in the metal film can cause a break to occur at a grain boundary. Moreover, the line-width roughness (LWR) from the patterned resist can result in deposited metal lines with a very high LWR, leading to an adverse change in device characteristics. Here a new approach that is not based on the lift-off technique but rather on low temperature hydrogen reduction of electron-beam patterned metal naphthenates is demonstrated. This not only enables the fabrication of sub-10 nm metal lines of good integrity, but also of low LWR, below the limit of 3,2 nm discussed in the International Technology Roadmap for Semiconductors. Using this method, sub10 nm nickel wires are obtained by reducing patterned nickel naphthenate lines in a hydrogen-rich atmosphere at 500°C for 1 h. The LWR (i.e., 3 σ_LWR) of these nickel nanolines was found to be 2.9 nm. The technique is general and is likely to be suitable for fabrication of nanostructures of most commonly used metals (and their alloys), such as iron, cobalt, nickel, copper, tungsten, molybdenum, and so on, from their respective metal-organic compounds.