Modeling of Precursors for Atomic Layer Deposition of Magnesium and Calcium Oxide

Abstract

We present a study of magnesium and calcium precursor molecules in order to predict which of them would be more successful in atomic layer deposition (ALD) of metal oxides. Precursor chemistry plays a key role in ALD, since precursors must be volatile, thermally stable, chemisorb on the surface, and react rapidly with existing surface groups. We investigate one aspect of this, surface reactivity between ligands and hydroxyl groups, via a gas-phase model with energetics computed at the level of density functional theory (DFT). The precursors with higher reactivity towards hydrolysis (and thus most potentially useful for ALD) are M(bae), M(Ph-nacnac) 2 , and M(tmtate), which is rationalized as due to strain, particularly in the cyclic ligands bae and tmtate. Calculated trends for Mg and Ca follow each other closely, reflecting the similar chemistry among group 2 metals.

A Quantum Chemical Descriptor for CVD Precursor Design: Predicting Decomposition Rates of TBP and TBAs Isomers and Derivatives

“…Ab initio quantum chemical approaches are an established tool for the prediction of precursor chemistry, or even describing all steps of CVD processes . They are also often used to complement experimental investigations, however, for the prediction of decomposition channels, tedious computation of reaction barriers and transition states for every compound accessible is necessary .…”

Density Functional Theory Predictions of the Composition of Atomic Layer Deposition-Grown Ternary Oxides

“…Gas-phase hydrolysis model As a model for the elimination of H-L from the surface, the gas-phase energetics for the hydrolysis of M(L) q may be calculated using quantum chemical methods 17,18 .…”

“…This is so time-consuming that it has been carried out for only a small selection of binary oxides so far . Instead, the approach taken here is to study a simple gas-phase model that describes the bond making and bond breaking essential to the surface reactions of interest, thus allowing a larger number of chemical systems to be considered. , The model takes no account of surface geometry or reaction pathways, other than the possibility of proton transfer (mechanism B) and ligand exchange (mechanism C).…”

Studying chemical vapor deposition processes with theoretical chemistry

“…The state of the art to 2012 is summarized in ref 62. Since then, our most recent atomic-scale simulations have revealed new details of the mechanism of oxide ALD [43], have accounted for the stoichiometry of ternary oxides [63], have assessed precursor ligands for alkaline earth metal oxides [64] and for copper metal [65] and have developed kinetic Monte Carlo models of film growth [66].…”