(Invited) Reaction Mechanisms in ALD of Ternary Oxides

Abstract

Reaction mechanisms underlying the atomic layer deposition (ALD) of ternary oxide films are investigated via the dependence of film stoichiometry on the sequence of ALD pulses. Data on film composition are brought together from experiments on five ternary oxide systems containing La, Mn, Ca, Fe, Sr, or Co, all using beta-diketonate ligands (thd) in the metal precursor and ozone as the oxygen source. These data are compared with the predictions from two possible reaction models: one where all ligands are combusted by ozone, the other where extra ligands are eliminated during the metal precursor pulse due to the availability of surface hydroxyl. The latter reaction is seen to be strongly dependent on the strength of the metal-ligand bond. Differences in cation charge also affect the stoichiometry. In this way, factors dictating the composition of ternary oxides are elucidated, opening the way to improved control of ALD processes and material properties.