Multiparameter and Parallel Optimization of ReaxFF Reactive Force Field for Modeling the Atomic Layer Deposition of Copper

X Hu and J Schuster and SE Schulz, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 28077-28089 (2017).

DOI: 10.1021/acs.jpcc.7b09948

In this study, we aim to develop a ReaxFF reactive force field for simulating the reaction mechanism of copper atomic layer deposition (ALD). To achieve this, we optimized the Cu/C, Cu/H, and Cu/N parameters of ReaxFF and extended the existing Cu potential to describe Cu/C/H/O/N interactions involved in Cu ALD. The parametrization procedure was implemented through an efficient multiparameter and parallel optimization scheme based on the Taguchi method. Using the newly developed Cu potential, we performed reactive molecular dynamics (RMD) simulations on an abbreviated ALD cycle using a Cu(Pr-i-amd)(2) (Pr-i- amd = N,N'-diisopropylacetamidinate) or Cu(dmap)(2) (dmap = dimethylamino- 2-propoxide) precursor with the H radical as a coreactant. In the first half-cycle, the Cu(Pr-i-amd)(2) precursor is found to adsorb dissociatively on the Cu surface as Cu(Pr-i-amd) monomers. During the second half-cycle, H radicals partly eliminate precursor fragments to the gas phase, but some intermediates such as C5H12N2 and C2H4N remain on the surface and may become a source of contamination. On the other hand, the Cu(dmap)(2) precursor dissociates into Cu(dmap) and dmap on the Cu surface. The second half-cycle is initiated through a hydrogen transfer reaction, which completely eliminates the dmap ligands to the gas phase. In general, our RMD simulations suggest that the surface chemistry of Cu(dmap)(2) during the ALD is simpler and cleaner than that of Cu(Pr-i-amd)(2).

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