Journal ArticleDOI
Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process
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In this paper, the surface chemistry of the trimethylaluminum/water ALD process is reviewed, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials.Abstract:
Atomic layer deposition(ALD), a chemical vapor deposition technique based on sequential self-terminating gas–solid reactions, has for about four decades been applied for manufacturing conformal inorganic material layers with thickness down to the nanometer range. Despite the numerous successful applications of material growth by ALD, many physicochemical processes that control ALD growth are not yet sufficiently understood. To increase understanding of ALD processes, overviews are needed not only of the existing ALD processes and their applications, but also of the knowledge of the surface chemistry of specific ALD processes. This work aims to start the overviews on specific ALD processes by reviewing the experimental information available on the surface chemistry of the trimethylaluminum/water process. This process is generally known as a rather ideal ALD process, and plenty of information is available on its surface chemistry. This in-depth summary of the surface chemistry of one representative ALD process aims also to provide a view on the current status of understanding the surface chemistry of ALD, in general. The review starts by describing the basic characteristics of ALD, discussing the history of ALD—including the question who made the first ALD experiments—and giving an overview of the two-reactant ALD processes investigated to date. Second, the basic concepts related to the surface chemistry of ALD are described from a generic viewpoint applicable to all ALD processes based on compound reactants. This description includes physicochemical requirements for self-terminating reactions,reaction kinetics, typical chemisorption mechanisms, factors causing saturation, reasons for growth of less than a monolayer per cycle, effect of the temperature and number of cycles on the growth per cycle (GPC), and the growth mode. A comparison is made of three models available for estimating the sterically allowed value of GPC in ALD. Third, the experimental information on the surface chemistry in the trimethylaluminum/water ALD process are reviewed using the concepts developed in the second part of this review. The results are reviewed critically, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials. Although the surface chemistry of the trimethylaluminum/water ALD process is rather well understood, systematic investigations of the reaction kinetics and the growth mode on different substrates are still missing. The last part of the review is devoted to discussing issues which may hamper surface chemistry investigations of ALD, such as problematic historical assumptions, nonstandard terminology, and the effect of experimental conditions on the surface chemistry of ALD. I hope that this review can help the newcomer get acquainted with the exciting and challenging field of surface chemistry of ALD and can serve as a useful guide for the specialist towards the fifth decade of ALD research.read more
Citations
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High dielectric constant gate oxides for metal oxide Si transistors
TL;DR: In this article, a review of the development of high-k gate oxides such as hafnium oxide (HFO) and high-K oxides is presented, with the focus on the work function control in metal gate electrodes.
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A brief review of atomic layer deposition: from fundamentals to applications
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Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends
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References
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Journal ArticleDOI
The mechanism of self-limiting growth of atomic layer epitaxy of GaAs by metalorganic molecular beam epitaxy using trimethylgallium and arsine
TL;DR: In this article, the self-limiting growth of atomic layer epitaxy by metalorganic molecular beam epitaxy using trimethylgallium (TMGa) and arsine (AsH3) was studied as a function of substrate surface condition.
Journal ArticleDOI
Adsorption and thermal reactions of disilane and the growth of Si films on Ge(100)-(2×1)
Abstract: Scanning tunneling microscopy (STM), core-level photoemission spectroscopy using synchrotron radiation, and electron diffraction were employed to study the vapor-phase epitaxial growth of Si on Ge(100)-(2\ifmmode\times\else\texttimes\fi{}1) using disilane (${\mathrm{Si}}_{2}$${\mathrm{H}}_{6}$). The dissociative chemisorption of a ${\mathrm{Si}}_{2}$${\mathrm{H}}_{6}$ molecule on Ge(100)-(2\ifmmode\times\else\texttimes\fi{}1) at room temperature results in two Si-trihydride (${\mathrm{SiH}}_{3}$) radicals bonded onto two adjacent Ge dangling bonds. Some ${\mathrm{SiH}}_{2}$ and GeH species are also formed as a result of decomposition of ${\mathrm{SiH}}_{3}$. An initial sticking coefficient of \ensuremath{\sim}0.5 is deduced from STM images. An exposure of more than 2 langmuirs (1 langmuir=${10}^{\mathrm{\ensuremath{-}}6}$ Torr s) of disilane at room temperature saturates the surface with ${\mathrm{SiH}}_{3}$, ${\mathrm{SiH}}_{2}$, and GeH species, and the resulting surface is disordered. The total amount of Si on the saturated surface is about 1/2 monolayer (ML). Successive annealing of the saturated surface to higher temperatures causes the conversion of ${\mathrm{SiH}}_{3}$ to ${\mathrm{SiH}}_{2}$, the conversion of ${\mathrm{SiH}}_{2}$ to SiH, and the desorption of H from GeH. These processes become complete at about 600 K, and the resulting surface is a clean Ge(100)-(2\ifmmode\times\else\texttimes\fi{}1) interspersed with about 1/2 ML of Si-monohydride (SiH)-(2\ifmmode\times\else\texttimes\fi{}1) islands. Desorption of hydrogen from these SiH islands occurs at even higher annealing temperatures, and is accompanied by indiffusion of Si into the Ge substrate. This process becomes complete at about 690 K, and the final system configuration is a clean Ge(100)-(2\ifmmode\times\else\texttimes\fi{}1) with about 1/2 ML of Si buried in the subsurface region. Multilayer Si deposition was performed by atomic layer epitaxy, i.e., cyclic disilane adsorption at \ensuremath{\sim}340 K followed by thermal conversion at 820 K. For up to 18 cycles, the resulting surface consists of Ge only. The change in surface morphology is studied by STM. Differences between the clean Si(100)-(2\ifmmode\times\else\texttimes\fi{}1) and Ge(100)-(2\ifmmode\times\else\texttimes\fi{}1) surfaces as observed by STM are also reported.
Journal ArticleDOI
Binding of chromium acetylacetonate on a silica support
A Hakuli,A Kytökivi +1 more
TL;DR: The binding of Cr(acac)3 vapor on silica pre-heated at 200, 560, and 820°C was studied between 160 and 240°C in a fixed bed flow reactor by determining the Cr and carbon concentrations, recording FTIR spectra and analyzing the thermal stability of the supported Cr complexes as discussed by the authors.
Journal ArticleDOI
Quantum Chemical Study of Zirconium Oxide Deposition on the Si(100)−(2×1) Surface
TL;DR: In this article, the atomistic mechanisms of two different deposition cycles are investigated: (1) ZrCl 4 is first deposited on the clean Si(100)-(2×1) surface.
Journal ArticleDOI
Deposition of AlN at lower temperatures by atmospheric metalorganic chemical vapor deposition using dimethylethylamine alane and ammonia
J. N. Kidder,Jason S. Kuo,A. Ludviksson,T. P. Pearsall,J. W. Rogers,John M. Grant,Lynn R. Allen,Sheng Teng Hsu +7 more
TL;DR: In this paper, an atomic layer growth process using amine-alane adducts as precursors for depositing aluminum nitride (AlN) thin films at temperatures between 300 and 800 K was carried out in a horizontal metalorganic chemical vapor deposition (MOCVD) reactor using H2 as a carrier gas.