Atomic Layer Deposition: An Overview

Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA.
Chemical Reviews (Impact Factor: 46.57). 11/2009; 110(1):111-31. DOI: 10.1021/cr900056b
Source: PubMed


Atomic layer deposition (ALD) which has emerged as an important technique for depositing thin films for a variety of applications has been reported. The necessity for continuous and pinhole-free films in semiconductor devices has driven the advancement of ALD. ALD is able to meet the needs for atomic layer control and conformal deposition using sequential, self-limiting surface reactions. The ALD of Al2O3 has developed as a model ALD system. ALD processing is also extendible to very large substrates and to parallel processing of multiple substrates. ALD is a gas phase method based on sequential, selflimiting surface reactions. ALD can deposit very conformal and ultrathin films on substrates with very high aspect ratios. ALD on high aspect ratio structures was then considered including an examination of the times required for conformal growth on high aspect ratio structures. The number of applications for ALD also continues to grow outside of the semiconductor arena.

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    • "ALD is one of the most rapidly developing fields of thin film technology belonging to the general class of chemical vapor deposition (CVD) techniques [4]. Typical applications for ALD-films include semiconductor devices such as high dielectric constant gate oxides in the MOSFET structure, copper diffusion barriers in backend interconnects , energy applications as well as micro-and nanoelectromechanical systems (MEMS/NEMS) [5] [6]. TiO 2 thin films are used in a wide variety of applications: photovoltaic devices such as solar cells [7] [8], corrosion resistance [9], self-cleaning [10], water purification [11], anti-fogging [12], superhydrophilicity [13], as well as anti-bacterial [14], -fungal [15] and -algal [16] applications. "
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    ABSTRACT: For every coating it is critical that the coatings are sufficiently durable to withstand practical applications and that the films adhere well enough to the substrate. In this paper the nanotribological, nanomechanical and interfacial properties of 15 - 100 nm thick atomic layer deposited (ALD) TiO2 coatings deposited at 110 - 300 °C were studied using a novel combination of nanoscratch and scanning nanowear testing. Thin film wear increased linearly with increasing scanning nanowear load. The film deposited at 300 °C was up to 58 ± 11 %-points more wear-resistant compared to the films deposited at lower temperatures due to higher hardness and crystallinity of the film. Amorphous/nanocrystalline composite structure with agglomerated crystallites was observed with TiO2 deposited at 200 °C and the agglomerates were up to 37 ± 10 %-points more wear-resistant than the amorphous/nanocrystalline matrix. All of the tested films had excellent interfacial properties and no delamination was observed with the films outside of the scanned regions. These findings may prove useful in the development of tribological and mechanical characterization methods, and in developing thin film materials with enhanced properties tailored to their function. This will also help in the development and tuning of ALD processes.
    Wear 09/2015; 342-343:270-278. DOI:10.1016/j.wear.2015.09.001 · 1.91 Impact Factor
    • "In the recent past, ALD coatings of TiO 2 , SiO 2 , and Al 2 O 3 were already successfully applied to different porous systems including AAO membranes [26] [27] [28] [29] [30]. Sander et al deposited TiO 2 layers of less than 3 nm thickness in 40 nm wide nanochannels in AAO (aspect ratio 38) [26]. "
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    ABSTRACT: Low-temperature atomic layer deposition (ALD) of TiO2, SiO2, and Al2O3 was applied to modify the surface and to tailor the diameter of nanochannels in etched ion-track polycarbonate membranes. The homogeneity, conformity, and composition of the coating inside the nanochannels are investigated for different channel diameters (18-55 nm) and film thicknesses (5-22 nm). Small angle x-ray scattering before and after ALD demonstrates conformal coating along the full channel length. X-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy provide evidence of nearly stoichiometric composition of the different coatings. By wet-chemical methods, the ALD-deposited film is released from the supporting polymer templates providing 30 μm long self-supporting nanotubes with walls as thin as 5 nm. Electrolytic ion-conductivity measurements provide proof-of-concept that combining ALD coating with ion-track nanotechnology offers promising perspectives for single-pore applications by controlled shrinking of an oversized pore to a preferred smaller diameter and fine-tuning of the chemical and physical nature of the inner channel surface.
    Nanotechnology 08/2015; 26(33):335301. DOI:10.1088/0957-4484/26/33/335301 · 3.82 Impact Factor
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    • "It is well known that electrodeposition on graphite does not proceed on the basal planes, but only at step edges or surface defects.[55] [56] The report concerning Ge x Sb y Te z formation by this group involved use of E- ALD.[47] Atomic layer deposition (ALD)[57], originally referred to as atomic layer epitaxy (ALE),[58] [59] is a group of techniques used to grow nanofilms of materials an atomic layer at a time. It is based on the use of surface limited reactions in a cycle to obtain atomic layer control over deposition. "
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    ABSTRACT: This paper will discuss possible formation of germanene electrochemically. Germanene should be a single layer allotrope of Ge. The techniques of in situ electrochemical STM (EC-STM), voltammetry, coulometry, and micro-Raman have been used to investigate the electrochemical formation of germanene. Studies on Au(111) show that the initial deposition of Ge is kinetically slow and somewhat unstable, whereas the self-limited layer of Ge is stable and shows atomic distances of about 0.44 nm ± 0.02 nm. Micro-Raman was performed on Ge nanofilms, but only displayed a shift near 290 cm-1 in one area. Given the STM results, it appears that the coherence of the germanene domains will need to be increased in order to more consistently produce the Raman signal. The data presented suggest that germanene has been formed electrochemically, although only as a minority species.
    ECS Transactions 05/2015; 66(6):129-140. DOI:10.1149/06606.0129ecst
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