Improving ALD growth rate via ligand basicity: Quantum chemical calculations on lanthanum precursors

At the atomic scale, the success of atomic layer deposition (ALD) depends on the efficient elimination of precursor ligands from the surface of the growing film. For the ALD of high-k lanthanum oxide films, we consider alkoxide, cyclopentadienyl, β-diketonate and amide precursors, and use density functional theory to compute their reactivity with respect to ligand elimination during ALD with water vapour. The energetic data are correlated with electronic properties and steric demand, allowing recommendations for precursor design to be made. Ligands that are weaker Lewis bases than Brønsted bases are shown to be more successful as components of ALD precursors.