Self-assembled monolayers as inhibitors for area-selective deposition: A novel approach towards resist-less EUV lithography

Abstract

Patterning below 10 nm with conventional techniques such as Litho-etch (LE*), a subtractive self-aligned multiple patterning process, suffers from limitations due to edge placement errors, decreasing throughput, complexity, pattern collapse, photoresist non-uniformity. Bottom-up processes for fabrication of nano devices by means of Area selective deposition (ASD) are peaking up over top-down approaches to mitigate most of the above-mentioned problems. One of the ways to achieve ASD of an hardmask is by using extreme ultra-violet (EUV, lambda-13.5 nm) lithography to single-step pattern self-assembled monolayers (SAM) on a photosensitive substrate (or layer) followed by atomic layer deposition (ALD). In this work, photo-catalytically active titanium oxide is considered as substrate for the deposition of organosilane SAMs of different chain length. Upon exposure to EUV, fragmentation of SAM's molecules is observed though a mechanism involving electron/hole pair exchange from TiO2. This induces changes in the chemistry of the exposed area, allowing an ALD deposition in the SAM-cleared areas.