Quantum Chemical Study of the Effect of Precursor Stereochemistry on Dissociative Chemisorption and Surface Redox Reactions During the Atomic Layer Deposition of the Transition Metal Copper

Abstract

Using quantum chemical calculations, we investigate surface reactions of copper precursors and diethylzinc as the reducing agent for effective Atomic Layer Deposition (ALD) of Cu. The adsorption of various commonly used Cu (II) precursors is explored. The precursors vary in the electronegativity and conjugation of the ligands and flexibility of the whole molecule. Our study shows that the overall stereochemistry of the precursor governs the adsorption onto its surface. Formation of different Cu (II) /Cu (I) / Cu (0) intermediate complexes from the respective Cu (II) compounds on the surface is also explored. The surface model is a (111) facet of a Cu 55 cluster. Cu (I) compounds are found to cover the surface after the precursor pulse, irrespective of the precursor chosen. We provide new information about the surface chemistry of Cu(II) versus Cu(I) compounds. A pair of CuEt intermediates or the dimer Cu 2 Et 2 reacts in order to deposit a new Cu atom and release gaseous butane. In this reaction, two electrons from the Et anions are donated to copper for reduction to metallic form. This indicates that a ligand exchange between the Cu and Zn is important for the success of this transmetalation reaction. The effect of the ligands in the precursor on the electron density before and after adsorption onto the surface has also been computed through population analysis. In the Cu (I) intermediate, charge is delocalized between the Cu precursor and the bare copper surface, indicating metallic bonding as the precursor densifies to the surface.

Classification of processes for the atomic layer deposition of metals based on mechanistic information from density functional theory calculations

“…21 The same redox behavior is computed to occur during the adsorption of other Cu(ii) precursors based on pyrrolylaldehyde N-isopropyl-2-pyrrolylaldiminate and 4N-(ethylamino)pent-3-en-2-onate ligands, as well as acac and dmap. 22 Charge is delocalized between the Cu precursor and the bare copper surface, indicating metallic bonding as the precursor densifies to the surface. It is computed that adsorption is stronger for those precursors with less steric hindrance, flexible ligands, and a planar geometry, because this allows access to surface atoms and the formation of strong metallic bonds.…”

Modeling Mechanism and Growth Reactions for New Nanofabrication Processes by Atomic Layer Deposition

“…Gas-phase energetics are used to screen possible surface intermediates, [ 80 ] which are then used in calculations of reaction pathways on a cluster model surface. [ 81 ] The role of precursor stereochemistry is examined and it is found that sterically hindered precursors have less chance of adsorption onto the surface. Pathways to incorporation of Zn impurity are identifi ed, explaining the experimental results.…”

Surface chemistry of copper metal and copper oxide atomic layer deposition from copper(ii) acetylacetonate: a combined first-principles and reactive molecular dynamics study

“…Recently, quantum chemistry (QC), in particular density functional theory (DFT) calculations, has become a powerful tool to explicit the ALD chemistry at an atomic scale. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] Dey et al 31 investigated the transmetalation reactions in Cu ALD using diethylzinc as the reducing agent, following experiments by Lee et al 8 Lin et al 32 have investigated the competition between ligand-exchange reactions and surface decomposition of Cu(acac) 2 on a Si(100)-2 Â 1 surface. More recently, we have studied the surface reactions of ( n Bu 3 P) 2 Cu(acac) and Cu(acac) 2 precursors on a Ta(110) surface.…”