Study of the initial surface reactions in atomic layer deposition of oxides, silicides and nitrides thin films on silicon substrates.

摘要

In this dissertation, key aspects of the surface chemistry associated with atomic layer deposition (ALD) are discussed. ALD is a novel and promising film deposition technique that can deliver precise thickness control at the angstrom or monolayer level; the self-limiting aspect of ALD makes it a unique method that can lead to excellent step coverage and conformal deposition on high aspect ratio structures. In spite of its central role in efficient film deposition processes, little is known about the mechanisms of the chemical reactions involved. Even the most basic information, such as the initial surface reactions, is in many instances unknown. There is a limited knowledge on the surface chemistry (e.g., substrate, precursor's reactivity) effects for the growth of the films. Reactivity in ALD is controlled by the nature of the substrate, where specific nucleation sites are often responsible for the initial deposition and where a change in chemistry may take place as the first layer of the growing film is formed. The precursor's reactivity towards the surface being used and its properties are fundamental aspects in an ALD process. The majority of the experiments discussed in this dissertation are devoted to the elucidation of the reaction mechanisms of the thin films. The experiments are carried out using in-situ Fourier transform infrared spectroscopy (FTIR) in order to examine the chemical composition of surface adsorbates. The use of in-situ characterization techniques is crucial for better control and understanding of thin film deposition. Knowledge of the surface chemistry underpinning the ALD processes is essential in order to design precursors in a rational way that will lead to successful film growth.