Download or read book Study of the Initial Surface Reactions in Atomic Layer Deposition of Oxides Silicides and Nitrides Thin Films on Silicon Substrates written by Karla Maria Bernal Ramos and published by . This book was released on 2014 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Atomic Layer Deposition for Semiconductors written by Cheol Seong Hwang and published by Springer Science & Business Media. This book was released on 2013-10-18 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: Offering thorough coverage of atomic layer deposition (ALD), this book moves from basic chemistry of ALD and modeling of processes to examine ALD in memory, logic devices and machines. Reviews history, operating principles and ALD processes for each device.

Download or read book Surface and Subsurface Reaction Mechanisms in Atomic Layer Deposition of Metals and Metal Oxides written by Joel Richard Schneider and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology has shown remarkable versatility and strength in response to large-scale challenges facing society today, despite many of its technical applications being on the atomic scale. From renewable energy devices to medical and sequencing technologies, to three-dimensional transistor architectures, advanced water purification, and novel organic-inorganic hybrid materials, nanotechnology has enabled powerful advances through precisely creating materials with specific chemistries and nanostructures. Thin films are particularly robust in their applications, and atomic layer deposition (ALD) is a thin film deposition technique with demonstrated strengths in precision, tunability, and structural control. The core principles of ALD that allow it to achieve these powerful results rely on self-limiting surface chemical reactions; however, despite the prevalence of ALD reports in the literature there are still many surface mechanisms that are poorly understood. ALD material properties can be highly sensitive to process conditions, impurities introduced from surface reactions, subtle changes in reaction rates, and many more phenomena, so it is critical to fully understand the surface reaction mechanisms at play in ALD to effectively implement processes and design chemistries for new materials. Especially as ALD is often idealized to behave in a simple self-limiting manner, the presence of more complex surface reactions that deviate from this behavior necessitates deeper study. As a result, this dissertation presents work to find, characterize, and model new reaction mechanisms in ALD that cause deviations from ideal behavior, then generalize that understanding and apply it to new chemical systems. The first half of the work focuses on activating surface species in the ALD of metal oxides. ALD of iron oxide using ozone is investigated as a case study, and we find that during the process ozone generates reactive oxygen species that migrate below the surface of the growing film where they are stored. The expansion of the ALD reactions beyond the surface of the film to a reservoir of active species in the subsurface region has a host of implications on the ALD process and the resulting material. The storage of reactive species results in high growth rates, and the physical movement of species through the film causes preferential crystalline rearrangement and film roughening. Further studies of nickel oxide ALD found related behaviors, indicating it grows by a similar mechanism of subsurface active species storage. In both cases, the oxygen species are reactive enough to activate surface combustion reactions, including in ALD of other materials grown on top of the reactive reservoirs. These mechanisms are consistent with reports of some other oxides, suggesting oxygen mobility and oxidizability of the metal center may be important factors in facilitating this reservoir mechanism. The second half of this thesis focuses instead on surface passivating species in metal ALD. As ALD hinges on self-limiting reactions resulting from the surface being passivated toward further reaction, the persistence of passivation is key to consistent and precise process function. A promising precursor for ruthenium ALD, Ru(DMBD)(CO)3, is studied due to its unique passivation mechanism of L-type ligands bonded to a zero-oxidation state metal center. Some reports have hypothesized this bonding results in excellent nucleation and growth properties, while others that it results in poor deposition control with better applications in continuous-deposition processes. By studying this ALD process, we can then gain insight into both surface passivation mechanisms and broader principles for process design of metals and zero-oxidation state compounds. We find the precursor undergoes a spontaneous decarbonylation reaction mechanism whereby the surface is initially passivated with carbonyl species that are lost with increasing temperature or time. Comparison of in situ characterization data and first principles kinetic modeling support these findings. Our results help explain inconsistencies in previous reports as well as observations of other zero-oxidation state precursors. Together, characterizing new surface mechanisms in ALD of both activating and passivating species gives a more complete picture of how a range of ALD processes can deviate from idealized and simplified self-limiting surface reactions. These findings span the breadth of both metal and metal oxide ALD, and we apply the insights to new ALD systems involving multicomponent and catalytically activated ALD processes. These grow the chemical toolbox of ALD and illustrate how a proper fundamental chemical understanding of ALD is important not only for effective implementation and control of existing processes but also for generalizing, expanding, and designing tools for ALD to further widen its horizons.

Download or read book Silicon Nitride Silicon Dioxide Thin Insulating Films and Other Emerging Diele c trics VIII written by Ram Ekwal Sah and published by The Electrochemical Society. This book was released on 2005 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chemistry of Atomic Layer Deposition written by Seán Thomas Barry and published by Walter de Gruyter GmbH & Co KG. This book was released on 2021-11-08 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book will help chemists and non-chemists alike understand the fundamentals of surface chemistry and precursor design, and how these precursors drive the processes of atomic layer deposition, and how the surface-precursor interaction governs atomic layer deposition processes. The underlying principles in atomic layer deposition rely on the chemistry of a precursor with a surface.

Download or read book Silicon Nitride and Silicon Dioxide Thin Insulating Films VII written by Electrochemical Society. Meeting and published by The Electrochemical Society. This book was released on 2003 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanistic Studies of Atomic Layer Deposition and Thermal Atomic Layer Etching Processes of Various Oxide Thin Films written by Rezwanur Rahman and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomic layer deposition (ALD) and atomic layer etching (ALE) will be the key techniques for sub10 nm node technology. Establishing a mechanistic understanding of the underlying surface chemistry is crucial for the optimization ALD/ALE processes and their use in microelectronics device fabrication. However, non-traditional reactions occurring concurrently with ALD/ALE complicate the deposition/etching process. Herein, several mechanisms are investigated for the ALD and thermal ALE of various oxide thin films. The first study demonstrates how the coreactant can affect the deposition process for TiO2 ALD from a cyclopentadienyl-based precursor. The next study highlights an important, but mostly overlooked, phenomenon of precursor/substrate reactivity during an ALD process. The third study describes the ALD of Sc2O3 thin films using a novel precursor with ozone. The final study reveals the limitations of thermal ALE processes for Al2O3 and SiO2 thin films, and proposes possible solutions to mitigate contamination issues inherent to the etching of these films. These investigations emphasize the need for surface-sensitive characterization techniques to unravel the complexities of these ALD/ALE processes.

Download or read book Chemical Solution Deposition of Functional Oxide Thin Films written by Theodor Schneller and published by Springer Science & Business Media. This book was released on 2014-01-24 with total page 801 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first text to cover all aspects of solution processed functional oxide thin-films. Chemical Solution Deposition (CSD) comprises all solution based thin- film deposition techniques, which involve chemical reactions of precursors during the formation of the oxide films, i. e. sol-gel type routes, metallo-organic decomposition routes, hybrid routes, etc. While the development of sol-gel type processes for optical coatings on glass by silicon dioxide and titanium dioxide dates from the mid-20th century, the first CSD derived electronic oxide thin films, such as lead zirconate titanate, were prepared in the 1980’s. Since then CSD has emerged as a highly flexible and cost-effective technique for the fabrication of a very wide variety of functional oxide thin films. Application areas include, for example, integrated dielectric capacitors, ferroelectric random access memories, pyroelectric infrared detectors, piezoelectric micro-electromechanical systems, antireflective coatings, optical filters, conducting-, transparent conducting-, and superconducting layers, luminescent coatings, gas sensors, thin film solid-oxide fuel cells, and photoelectrocatalytic solar cells. In the appendix detailed “cooking recipes” for selected material systems are offered.

Download or read book Silicon Nitride and Silicon Dioxide Thin Insulating Films written by M. Jamal Deen and published by The Electrochemical Society. This book was released on 1997 with total page 610 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Selective Chemistry of Metal Oxide Atomic Layer Deposition on Si Based Substrate Surfaces written by Lei Guo and published by . This book was released on 2015 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: A versatile home-made atomic layer deposition (ALD) reactor was designed and built in our lab. This reactor can be used to deposit metal oxides on both wafer substrates and porous inorganic particles. Also, a simple procedure for selective ALD has been developed for the processing of silicon wafers in order to facilitate the spatially resolved growth of thin solid films on their surfaces. Specifically, a combination of silylation and UV/ozonolysis was tested as a way to control the concentration of the surface hydroxo groups required for subsequent atomic layer deposition (ALD) of metals or oxides. Water contact angle measurements were used to evaluate the hydrophilicity/hydrophobicity of the surface, a proxy for OH surface coverage, and to optimize the UV/ozonolysis treatment. Silylation with silanes was found to be an efficient way to block the hydroxo sites and to passivate the underlying surface, and UV/O 3 treatments were shown to effectively remove the silylation layer and to regain the surface reactivity. Both O3 and 185 nm UV radiation were determined necessary for the removal of the silylation layer, and additional 254 nm radiation was found to enhance the process. Attenuated total reflection-infrared absorption spectroscopy was employed to assess the success of the silylation and UV/O 3 removal steps, and atomic force microscopy data provided evidence for the retention of the original smoothness of the surface. Selective growth of HfO2 films via TDMAHf + H2 O ALD was seen only on the UV/O3 treated surfaces; total inhibition of the deposition was observed on the untreated silylated surfaces. We believe that the silylation-UV/O 3 procedure advanced here could be easily implemented for the patterning of surfaces in many microelectronic applications.

Download or read book The Initial Stages of Atomic Layer Deposition on Substrates Modified by Organic Thin Films written by Kevin James Hughes and published by . This book was released on 2011 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomic layer deposition (ALD) provides the ability to deposit highly conformal thin films with essentially molecular level control over film thickness. These characteristics have made it an active area of research for a number of applications, notably in the field of semiconductor devices. The focus of the work presented here is on the initial stages of film growth, including the first interaction of gas phase ALD precursors with the substrate, and the period in which the growing surface transitions from the starting substrate to the steady-state growing film. Of particular interest are substrates modified using thin organic films. These organic films are used to alter the identity, density and spatial extent of functional groups on the surface. We begin with a review of the prior work in this area, focusing on the ALD of TiNx on a variety of organic films, including self-assembled monolayers with various endgroup chemistries, and branched films with a more 3-d distribution of functional groups. Here connections are observed between the initial interactions of the gas phase precursors with the organic film, and the subsequent stages of ALD growth. A relationship between the initial rate of ALD growth and the resulting film morphology is also observed, and can be explained by a variation in nucleation site density due to the structure of the organic film. The next section involves the ALD of a range of materials (Al2O3, HfO2, Ta2O5, and TaNx), on a single organic layer, branched poly(ethylene imine) (PEI). Here, the presence of the organic layer causes an attenuation in the amount of material deposited per ALD cycle in the initial stages of growth. A strong correlation was found between the thermodynamic driving force of the ALD reaction and the degree of attenuation, suggesting that ALD processes in which there is a strong driving force (or low activation energy) for the formation of the final products can more easily overcome the obstacles presented by the organic layer. The ALD of one material, TaNx, was examined in more detail using in situ XPS. Substrates in this study included nonporous SiO2, a porous low dielectric constant or 'low-[kappa]' material, and both substrates modified by PEI films. PEI was used here in part because of the tendency of smaller molecules to infiltrate and deposit within the pore network of the low-[kappa]. The chemical structure of the chemisorbed tantalum precursor, Ta[N(CH3)2]5, after the first cycle of ALD, as well as the oxidation state and chemical composition of the TaNx film in the first 10 cycles (~ 610 Å) were strongly affected by the starting substrate. Substrates with a high density of oxygen containing groups led to a more oxidized TaNx film, and less efficient incorporation of N in a nitride binding state. Furthermore, the presence of a PEI film enhanced the growth of TaNx at the surface of the porous low-[kappa], and limited infiltration of the pore network by the gas phase ALD precursors. A final set of experiments involved the early stages of cobalt film formation on tantalum substrates using chemical vapor deposition with the metalorganic precursor dicobalt hexacarbonyl tert-butylacetylene (CCTBA). Here it was found that growth proceeded in two phases. The first involved the formation of an intermixed cobalt/tantalum layer, while the second took place after the intermixed layer was covered and was characterized by the formation of a mixed carbon/cobalt film.

Download or read book Atomic Layer Deposition ALD written by Callisto Joan MacIsaac and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern society demands smaller, more precise devices for both microelectronic and energy technologies. The development of methods and processes that can deposit reliably uniform, conformal thin films on the nanoscale is essential to fields as diverse as catalysts and solar cells. Therefore, atomic layer deposition (ALD), a thin-film deposition technique that accomplishes these goals by using self-limiting sequential reactions between alternating precursors to achieve atomic precision over the product film, is an important tool for the modern era. Combining ALD with molecular layer deposition (MLD), which follows the same principles as ALD but deposits entire organic molecules to build films, results in a powerful system that enables the deposition of inorganic, organic, and hybrid inorganic-organic materials. Understanding the nucleation mechanisms, surface reaction chemistry, and applications of these materials and ALD/MLD processes is essential to commercialization and wider use. Through in situ Fourier transform infrared (FTIR) spectroscopy, we studied the zinc-tin-oxide (ZTO) system, a ternary ALD process that is a combination of the zinc oxide and tin oxide binary ALD processes. Previous research had indicated that the ternary system is characterized by non-idealities in the ALD growth, and we identify as a potential cause of these effects incomplete removal of the ligands from the tetrakis(dimethylamino)tin precursor, which leads to a nucleation delay when depositing ZnO on SnO2. A significant fraction of the ligands remain on the surface during the ALD of SnO2 and endure when the process is switched to ZnO ALD. This result suggests that the occupation of surface reactive sites by these persisting ligands may be the cause of the observed nucleation delay with potential ramifications for many other binary and ternary systems where persisting ligands may be present. In addition, we studied the mechanism of ALD-grown MoS2 thin films. It was observed by atomic force microscopy (AFM), grazing incidence small angle X-ray scattering (GISAXS), and X-ray reflectivity (XRR) that nucleation proceeds by the formation of small islands that coalesce into a complete film in under 100 cycles, with further film growth failing to occur after coalescence. This inertness is attributed to the chemical inactivity of the basal planes of MoS2. It was found that the final thickness of the as-grown film is not determined by the number of ALD cycles as per the normal regime, but by the temperature that the film is deposited at. This self-limiting layer synthesis (SLS) has been reported in the literature for higher temperature depositions of MoS2, but this is the first report of the effect in a low temperature, amorphous MoS2 ALD system. The thickness of films growth by ALD with the precursors Mo(CO)6 and H2S was found to saturate at around 7 nm on both native oxide-covered silicon and bulk crystalline MoS2 substrates, which may indicate that the SLS behavior is inherent to the ALD process and not substantially a product of the substrate surface potential. Finally, we demonstrated a new ALD/MLD hybrid process that used the MoS2 ALD precursor Mo(CO)6 and the counter reagent 1,2-ethanedithiol to create a MoS2-like material with organic domains. This Mo-thiolate possesses many properties that link it to MoS2, such as activity towards the hydrogen evolution reaction (HER) and similar Raman modes, but has a significantly lower density, optical transparency, and higher geometric surface area. It was found that the process has a 1.3 Å growth per cycle and can catalyze the HER reaction at an overpotential of 294 mV at -10 mA/cm2 , which is superior to planar MoS2 and ranks the as-deposited catalyst with the best nanostructured MoS2-based catalysts. We propose that this activity comes from the higher surface area induced by the incorporation of organic chains into the films. In summary, we explored the mechanisms and nucleation behavior of several ALD systems of interest to energy applications using both in situ and ex situ analysis techniques. These studies demonstrated the importance of understanding ALD surface chemistry to the overall chemical composition of the resultant films, the ramifications of different nucleation regimes in determining morphologies, and the power of ALD/MLD in creating analogues to previously known species with improved physical properties.

Download or read book Proceedings of the Symposium on Silicon Nitride and Silicon Dioxide Thin Insulating Films written by Vikram J. Kapoor and published by . This book was released on 1987 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Surface Modeling of Thin Film Growth written by Hee-Chuen Cho and published by . This book was released on 1993 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Publications of the National Institute of Standards and Technology Catalog written by National Institute of Standards and Technology (U.S.) and published by . This book was released on 1994 with total page 1162 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atomic Layer Deposition for Surface Modifications and Solid Film Fabrication written by Haoming Yan and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Along with the unceasing development of the surface and material science, modification of substrates surfaces in nanoscale, to fabricate the functional materials with precisely controlled dimensions, refined composition and desired properties becomes crucial. In this report, atomic layer deposition (ALD), a vapor phase, sequential and self-limiting deposition process, has been used as an alternative strategy to modify the surface of materials and fabricates nanometer or micrometer level of functional materials with precise control. In the first part of this dissertation, ALD was used to modify the surface of the shape-engineered nanocrystals (SENCs), which enhanced the thermal stability of the SENCs from 300?C to 700?C and enhanced the catalytic activities of the nanocrystals as well. We also proposed a new reaction mechanism of metal-organic precursor with oxide surface, in which the conventional layered ALD growth does not happen but the oxide surface was modified via controlled metal doping. In the second part of this dissertation, ALD precursors were used to reacting with liquid substrates to fabricate freestanding solid thin films. Benefits from the unique reaction mechanism of the ALD metal-organic precursors, the thickness and the compositions of the fabricated films can be controlled. The fundamental of gas-liquid reaction has been discussed in this study. In the third part of this dissertation, area-selective ALD (AS-ALD) has been reported using carboxylic acid self-assembled monolayer as a growth inhibitor. Excellent selectivity of AS-ALD has been achieved by using this method, which could potentially be used in microfabrication as a substitution step for photolithography.