Non-growth ligand exchange reactions in atomic layer deposition of HfO 2

Abstract

We use density functional theory (DFT) to investigate non-growth ligand exchange reactions (NGLE) during the precursor half-cycle of atomic layer deposition (ALD) of HfO 2 using HfCl 4 and H 2O as part of a detailed atomistic mechanism. The non-growth ligand exchange (NGLE) reactions of HfCl 4 on as-grown OH terminated HfO 2 involve the formation of hydroxychlorides and dihydroxychlorides and have lower activation barriers compared to ligand exchange reactions, suggesting that these side-reactions are significant and competitive with ligand exchange. Consequently, NGLE reactions are predicted to be a significant source of chlorine contamination of HfO 2 ALD films deposited using HfCl 4 and can reduce the efficiency of metal deposition of the ALD process. However, on OH terminated SiO 2 these NGLE reactions are predicted to have appreciably larger barriers than ligand exchange reactions and consequently play a less significant role for the initial deposition of HfO 2 on SiO 2 substrates.