Tungsten nanocrystals embedded in high-k materials for memory application
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The formation of tungsten nanocrystals (W-NCs) on atomic-layer-deposited HfAlO∕Al2O3 tunnel oxide was demonstrated for application in a memory device. It was found that the density and size distribution of W-NCs are not only controlled by the initial film thickness, annealing temperature, and time, but also by the metal∕tunnel oxide interface structure. Well-isolated W-NCs with an average diameter of 5 nm and a surface density of 5×1011cm−2 were obtained by applying a thin Al2O3 wetting layer onto HfAlO tunneling oxide. A large flatband voltage shift of 5.7 V was observed from capacitance–voltage measurement when a bias voltage up to ±4V was applied.Keywords:
Wetting layer
Biasing
Conformal coating
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Physical vapor deposition
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Abstract Atomic layer deposition (ALD) is well known as the most advanced coating technique so far due to its unique deposition characteristics, such as uniformity and 3D conformality. ALD is not limited to coating technologies alone; however, over the past few decades, it has been extended beyond coating technologies to address several bottlenecks in the semiconductor industry. This short review article provides a summary of previous studies published on various approaches to using ALD to overcome the technological challenges in Si device fabrication beyond, that is, ALD for multiple patterning, area‐selective atomic layer deposition, atomic layer etching, and ALD for dry photoresist. The purpose of this review is to determine the existing trend in ALD for noncoating applications and to understand and provide a layout of what ALD can bring in the future. In addition, it helps in appreciating the potential of ALD in existing and future noncoating processes. Furthermore, this study provides a developing route for ALD in other noncoating applications in the semiconductor industry. This review may help ALD researchers in its use in various noncoating processes in the future to extend Moore's law.
Semiconductor Industry
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Atomic layer epitaxy
Photoresist
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We review our recent results on using Atomic Layer Deposition (ALD) in fabrication of nanophotonic waveguide devices. ALD is a unique thin film deposition method providing atomic level control of film composition and thickness, perfect step coverage, and large-area uniformity. We employ the advantages of ALD in connection with Sinanophotonics. We present several new structures based on filling silicon slot waveguides or coating the silicon strip waveguides with ALD-grown materials. Also ALD grown TiO2 strip waveguides are introduced.
Nanophotonics
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Waveguide
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The nucleation and growth of Pt atomic layer deposition (ALD) on Al2O3 substrates was studied using (methylcyclopentadienyl)-trimethyl platinum (MeCpPtMe3) and O2 plasma as the reactants. The nucleation of Pt ALD was examined on Al2O3 ALD substrates at 300 °C using a variety of techniques including spectroscopic ellipsometry, x-ray reflectivity, x-ray photoelectron spectroscopy, and scanning electron microscopy. These techniques revealed that Pt ALD does not nucleate and grow immediately on the Al2O3 ALD substrates. There was negligible Pt ALD during the first 38 ALD cycles. The Pt ALD growth rate then increased substantially during the next 12 ALD cycles. Subsequently, the Pt ALD growth rate reached a steady state linear growth regime for >50 ALD cycles. These measurements suggest that the Pt ALD first forms a number of nanoclusters that grow slowly during the first 38 ALD cycles. These islands then merge during the next 12 cycles and yield a steady state Pt ALD growth rate of ∼0.05 nm/cycle for >50 ALD cycles. The Pt ALD film at the onset of the steady state linear growth regime was approximately 2–3 nm in thickness. However, the SEM images of these Pt ALD films appeared corrugated and wormlike. These films also had a density that was only 50–70% of bulk Pt. Film densities that were consistent with bulk Pt were not observed until after >100 ALD cycles when the Pt ALD films appeared much smoother and were 4–5 nm in thickness. The Pt ALD nucleation rate could be enhanced somewhat using different O2 plasma parameters.
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The electronic properties of metal nanocrystal quantum dot solids in the insulating state have been measured as a function of nanocrystal diameter under conditions of controlled inter-nanocrystal separation. Such properties of these weakly coupled nanocrystal arrays (see image), in particular the array charging energy, can be manipulated through experimental control of the nanocrystal diameter and mean inter-nanocrystal separation.
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Atomic layer deposition (ALD) is a technique capable of producing ultrathin conformal films with atomic level control over thickness. A major drawback of ALD is its low deposition rate, making ALD less attractive for applications that require high throughput processing. An approach to overcome this drawback is spatial ALD, i.e., an ALD mode where the half-reactions are separated spatially instead of through the use of purge steps. This allows for high deposition rate and high throughput ALD without compromising the typical ALD assets. This paper gives a perspective of past and current developments in spatial ALD. The technology is discussed and the main players are identified. Furthermore, this overview highlights current as well as new applications for spatial ALD, with a focus on photovoltaics and flexible electronics.
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Atomic layer epitaxy
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Atomic Layer Deposition (ALD) is well known for its high film quality and high conformality, but limited by the low deposition rate. Beneq proposes a novel approach using Rotary Spatial Plasma Enhanced ALD process, which can reach deposition rates 10× higher than traditional pulsed ALD. This technology also enables use of PEALD in batch mode with high throughput. This paper describes the technology in more details.
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Abstract Atomic layer deposition (ALD) is known for depositing ultra-thin film materials that enable control of composition, highly conformal film, desirable thickness, self-saturating, and uniform deposition, and this review has established its evolvement in recent times. The ALD techniques have made more device applications possible in energy storage, solar cells, memory storage, catalysis, sensors, and many more. Its advantages and disadvantages for different modes were emphasized and the precursors used for several ALD processes were highlighted. The bibliometric approach used in this review has also revealed how ALD has evolved through the assessment of published documents, journals, authors, organizations, sponsors, and countries. The method also revealed that ALD research is limited in Africa, however, the first two ALD facilities were confirmed to be acquired by T.C. Jen at the University of Johannesburg, which will in turn burst ALD material research in Africa. The current study has provided researchers with a choice when considering using the ALD technique and in terms of research collaborations. It concluded by highlighting the challenges and future perspectives of ALD and bibliometric technique.
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