Detailed Atomistic Modeling of Si(110) Passivation by Atomic Layer Deposition of Al2O3

Abstract

Typical structural defects were studied theoretically in the course of O → Al → O atomic depositions on the basic Si(110) surface. The defects were determined by analyses of the band gap states and projected densities of the s- and p-states after the deposition aimed to form a Si(110)/SiOX/AlOY/γ-Al2O3 slab. The extent of Si(110) passivation after every deposition step was studied by scanning the band structure calculated using Density Functional Theory with periodic boundary conditions. The atomic structure of the optimized Si(110) surface was compared to the one of Si(100) for which more information is available. Our modeling reproduces most features of the use of trimethylaluminium or any other organic ligand as Al precursor along O2 plasma assisted atomic layer deposition (PA ALD) when the organic ligands are completely oxidized so that their participation can be neglected in the deposition as already shown experimentally. The final oxidation step corresponds to the junction of the slab deposited over Si(110) with a γ-Al2O3 fragment, whose super cell (SC) parameters have been selected to lead to the minimum mismatch. Different examples of either non-satisfactory or accurate junction of the oxidized Si(110) slab and γ-Al2O3 fragment (under two different forms) are discussed aiming to develop a route for understanding the dominant defect types at the interface. Such theoretical work should be the first step for the elaboration of computational tools for the passivation of silicon with amorphous oxides. The latter are mainly formed at the conditions of the PA ALD depositions. The list of formed typical defects at the Si(110)/SiOX/AlOY/γ-Al2O3 boundary is presented and characterized by the projected density of states and respective band structure around the band gap.