Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends

Abstract

Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas–solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic–organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.

Atomic-Level Structural and Electronic Properties of Hybrid Inorganic–Organic ZnO:Hydroquinone Superlattices Fabricated by ALD/MLD

“…ALD (Atomic Layer Deposition), for inorganic materials. [1][2][3] For the inorganicorganic hybrids, ALD cycles are combined with MLD (Molecular Layer Deposition) cycles based on purely organic precursors, [4][5][6][7] as schematically shown in Figure 1. This enables the atomic/molecular layer-by-layer production of inorganic-organic hybrid thin films through sequential self-limiting gas-surface reactions with high precision for the film thickness and composition like in the case of inorganic ALD thin films.…”

Enhanced Barrier Performance of Engineered Paper by Atomic Layer Deposited Al2O3 Thin Films

“…Atomic layer deposition (ALD) is a chemically versatile, layer by layer thin film deposition process which has been widely employed to deposit thin films of various materials 8,12,13 .…”

“…This method is proven to create densely packed and uniform films with low defect density, precise thickness, and low impurity contamination [12][13][14][15] . In addition, ALD is a dry method.…”

UHV and Ambient Pressure XPS: Potentials for Mg, MgO, and Mg(OH)2 Surface Analysis

“…53 Under realistic deposition conditions, the chemistry deviates from the ideal situation, including incomplete precursor reaction, contamination, precursor side reactions, film/substrate mixing, and non-uniform growth. To improve ALD and extend it to other materials, a better understanding of surface chemical mechanisms is required.…”

“…Atomic layer deposition (ALD) is a thin film deposition method for, e.g., metals and metal oxides, nitrides and sulfides, 53 which relies on the surface reactions of two or more alternating gas phase precursors to homogenously coat a surface with precise thickness control, assuming the reactions are complete and self-limiting. 53 Under realistic deposition conditions, the chemistry deviates from the ideal situation, including incomplete precursor reaction, contamination, precursor side reactions, film/substrate mixing, and non-uniform growth.…”