Scaling and Scale Up Effects during Area Selective Deposition using Self-Assembled Monolayers and Small Molecule Inhibitors

Area selective deposition (ASD) is a promising bottom-up patterning approach that has attracted significant interest in microelectronics. Area selective deposition methods can be roughly divided into two classes: intrinsically selective processes, which take advantage of preferential reactivity of precursors, and processes based on surface passivation. While growth selectivity is often used as a benchmark to quantify the performance of an ASD process, the scalability of ASD both in terms of pattern size (scaling) and substrate size (in terms of area and aspect ratio) is comparatively less understood.<br/><br/>In this presentation, I will focus on two case studies that explore the scalability of different area selective deposition approaches: the first example explores the impact of pattern size on the stability and density of defects of self-assembled monolayers (SAMs). SAMs exhibit a range of dynamic behaviors that can greatly affect their effectivity blocking precursors: these include order/disorder transitions, non-negligible surface mobility, or the presence of so-called gauche defects. Using simple dynamic models, we have explored how pattern size affect the stability of SAMs, and how, depending on chain-chain and surface interactions, size effects can lead to substantial changes on the areal density and distributions of defects in SAMs.<br/><br/>In the second example, I focus on how heterogeneous processes during small molecule area selective deposition can affect the scale up of area selective deposition to large scale (i.e. wafer size) and high surface area (i.e. high aspect ratio) substrates. A key aspect of area selective deposition processes using small molecule inhibitors is the need of effectively remove them from the substrate after each ALD cycle. Through a combination of in-situ characterization techniques, kinetic models, and transport models both within features and at the reactor scale, we have explored the impact that surface kinetics has on the elimination of inhibitor molecules. Our results show that reversibility in the inhibition process can greatly increase the purge times required to effectively remove inhibitors from large area substrates, creating inhomogeneities in film thickness even when processes are fully self-limited.<br/><br/>These two examples exemplify the tight coupling between the fundamental aspects of area selective deposition processes and their behavior under conditions relevant for semiconductor manufacturing.