A density functional theory study of alumina atomic layer deposition on alumina and silica

Atomic layer deposition (ALD) is a thin film deposition process based on alternating exposure of precursor materials on a substrate surface. If the former are chosen in an appropriate way, alternate sequential exposure of precursors results in self-terminating reactions and thus allows a controlled layer-by-layer growth. Therefore ALD has been applied for deposition of high-k dielectric material such as alumina in the micro-electronics industry. In this work, the alumina atomic layer deposition process has been investigated. The success of ALD rests on its chemistry. It is thus important to identify and understand the underlying elementary reactions responsible for ideal film growth and those reactions that can lead to undesired impurities in the films. Experimental investigations have been conducted in an attempt to explain the mechanism of ALD. However, atomic scale simulations can be an effective way to examine mechanisms in more detail. To this end, in this work, Density Functional Theory (DFT) calculations have been used to explore the elementary reactions and the possible intermediates have been validated by comparing calculated vibrational frequencies with experimental values. In this way, a more detailed understanding of alumina ALD mechanism is obtained