Area-Selective ALD with Soft Lithographic Methods: Using Self-Assembled Monolayers to Direct Film Deposition

Area-selective atomic layer deposition (ALD) is a technique that can be used for fabricating 3D structures with dimensions down to the nanoscale. A patterned resist, typically a self-assembled monolayer (SAM), directs film deposition through area-selective ALD, leading to lateral patterning. This article will describe the overall approach to area-selective ALD, introduce the process of atomic layer deposition, and discuss the development of monolayer ALD resists. We will describe the results of studies which show that monolayers with a high degree of packing and hydrophobicity perform best in blocking ALD, and that resistance against ALD can be used as a sensitive probe of SAM quality. We further describe patterning of the SAM through soft lithography, in particular microcontact printing (mu CP), for the area-selective ALD process, and compare the area-selective ALD processes for HfO2 and Pt ALD. The powerful patterning capability of mu CP and the flexibility of area-selective ALD for various materials can impact many potential applications, and studies applying this process to fuel cell devices and integrated circuits will be described.