Reaction mechanisms of chlorine reduction on hydroxylated alumina in titanium nitride growth: First principles study

Abstract

The nature of the electronic interaction of precursor molecules with functionalized surfaces are still uncertain. Here, DFT calculations were performed to study the dissociative reactions of TiCl4 on non-hydroxylated and hydroxylated α-Al2O3 (0 0 0 1) surface based on DFT calculation. For non-hydroxylated α-Al2O3 (0 0 0 1) surface, residual Cl atoms from the dissociative reactions hinder another TiCl4 molecule to be adsorbed on non-hydroxylated α-Al2O3 surface, which are known to greatly degrade the performance of memory devices. We found that the removal of those Cl adatoms is energetically difficult on the non-hydroxylated α-Al2O3 (0 0 0 1) surface due to the strong bonding nature of ClAl bond, which was additionally confirmed by charge density difference and Bader charge analysis. In contrast, hydroxyl functional group worked as a catalysis for the dissociative reactions of TiCl4 molecules by lowering activation energy for the successive removal process of Cl adatoms as HCl gas on the hydroxylated surface. These results imply that the electronic interaction between highly reactive molecule and surface functional group should be deeply understood in order to design the ALD process of future memory devices.