Fabrication of Sub‐10 nm Metallic Lines of Low Line‐Width Roughness by Hydrogen Reduction of Patterned Metal–Organic Materials

Abstract

The fabrication of very narrow metal lines by the lift‐off technique, especially below sub‐10 nm, 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, sub‐10 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 σLWR) 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.

Delineating the pathways for the site-directed synthesis of individual nanoparticles on surfaces

“…S7). It is important to note here that many of the particles formed through pathway 3 exist as metal oxides under ambient conditions, and in principle, they could be annealed under a reducing atmosphere to obtain metal nanoparticles (29). Furthermore, metal alloy nanoparticles (for instance, of Au and Ag) can also be synthesized by simply blending the metal precursors in the ink, showing the versatility of the method (Fig.…”

Metal hierarchical patterning by direct nanoimprint lithography

“…Till date, such routes using metal-organics as lithography resists, have been employed for simple two-dimensional patterning of metals by direct write electron beam lithography1011 and micromolding1213. For large area patterning, nanoimprint lithography (NIL) is ideal14, although direct imprinting of metal patterns has not been attempted thus far; there are examples related to metal oxides using precursors such as metal methacrylates15 and alkoxides161718.…”

Direct Patterning of TiO2 Using Step-and-Flash Imprint Lithography

“…Furthermore, it may be possible to fabricate metal nanostructures by hydrogen reduction of metal oxides that reside above the water formation line in the Ellingham diagram. 44 However, our resist does suffer from a drawback: its deep brown color results in loss of UV radiation due to absorption by the complex in the TiO 2 resist. This results in longer exposure time, thereby, adversely affecting the lifetime of the antisticking layer on the template surface.…”

“…Lastly, our approach can easily be extended to fabricate functional nanostructures of other metal oxides as well. Furthermore, it may be possible to fabricate metal nanostructures by hydrogen reduction of metal oxides that reside above the water formation line in the Ellingham diagram …”