Exploring selective Atomic Layer Deposition of metals for molecular Field-Coupled Nanocomputing prototyping

The advancement of nanofabrication techniques is essential for meeting the escalating demands of the semiconductor industry in terms of device miniaturization and performance enhancement. This study focuses on exploring deposition techniques, particularly selective Atomic Layer Deposition (ALD), to propose a feasibility study of molecular Field-Coupled Nanocomputing (molFCN) devices preliminary prototyping. The primary objective is to demonstrate deposition selectivity on substrates with different terminations to enable precise metallic pattern deposition for molFCN fabrication. Specifically, the study examines the potential barriers of half-reactions during ALD of metals (Au, Cu, and Pt) on silicon substrates either stripped or with -H and -OH terminations. The analysis has been carried out through Ab initio geometry optimizations, Nudge Elastic Band analysis, and Molecular Dynamics simulations utilizing Orca and QuantumATK as computational tools. The findings reveal variations in potential barriers influenced by the interactions between chosen precursors and the substrate terminations. Specifically, the insights gained into precursor-substrate interactions and the effectiveness of hydrogen passivation revealed that the dangling bonds on the stripped silicon substrate are more reactive than their passivated counterpart, the evidence for this preferential behaviour is evident for Au, less so with Cu and Pt. These findings offer valuable contributions to nanopatterning processes despite the adopted approximations in results due to computational constraints and complexities. Moreover, this analysis provides ground for further investigation potentially addressing the existing gap in the literature on the topic. Future studies are necessary to evaluate the scalability and sustainability of the proposed techniques to extend the study to larger and more complex samples. Moreover, great emphasis goes to the need for comprehensive force field evaluations to address challenges encountered in molecular dynamics simulations. Additionally, the instability and reactivity of some precursors posed unexpected challenges, therefore further investigation on precursor synthesis stability to improve computational analysis and data reliability.