A reliable scheme for fabricating sub-5 nm co-planar junctions for single-moleculeelectronics

Abstract

We demonstrate a high yield production scheme to fabricate sub-5 nmco-planar metal–insulator–metal junctions. This involves determining therelationship between the actual gap between the metallic junctions fora given designed gap, and the use of weak developers with ultrasonicagitation to process the exposed resist. This results in an improved process toachieve narrow inter-electrode gaps. The gaps were imaged using an AFMequipped with a carbon nanotube tip to achieve a high degree of accuracyin measurement. The smallest gap unambiguously measured was ∼ 2 nm. Gapswith ≤5 nm spacing were produced with a very high yield of about 75% fora designed inter-electrode distance of 0 nm. The leakage resistanceof the gaps was found to be of the order of 1012 Ω. Theentire junction structure was designed to be co-planar to better than 1 nm over 1μm2.