Multiscale Simulations of ALD in Cross Flow Reactors

Two of the biggest challenges in reactor-scale simulations of ALD processes are our lack of knowledge on the mechanistic details of surface chemistry and the need to integrate reactor scale and feature scales in the simulations. In order to assist our process development and scale up we have developed a multiscale simulation code that allows us to study the impact of surface chemistry on the coating of large area substrates with high surface area/high aspect-ratio features. Our code, based on open-source libraries, takes advantage of the ALD surface chemistry to achieve an extremely efficient two-way coupling between reactor and feature length scales, and it can provide simulated quartz crystal microbalance and mass spectrometry data at any point of the reactor. By combining experimental surface characterization with simple analysis of growth profiles in a tubular cross flow reactor, we are able to extract a minimal set of reactions to effectively model the surface chemistry, including the presence of spurious CVD. These reactions are then used as an input for the large-scale 3D simulations. In this work, we will focus on two aspects of the problem: the impact of non-ideal surface chemistry and the role of reactor geometry in the coating of both planar and high surface area substrates. Finally, we will discuss the impact of moving substrates characteristic of roll-to-roll processes.