Slides of my first invited talk at a conference, the ALD 2005 conference in San Jose 2005, about ALD modelling. ALD is fantastic, but fantastic is not perfect :)
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R. L. Puurunen, Atomic-scale modelling of atomic layer deposition processes, American Vacuum Society Topical Conference on Atomic Layer Deposition (ALD 2005), San Jose, California, August 8-10, 2005. Invited talk.
Slides of an invited talk, given at EuroCVD in 2007
R. L. Puurunen, Understanding the surface chemistry of atomic layer deposition: achievements and challenges, Sixteenth European Conference on Chemical Vapor Deposition, EuroCVD-16. Den Haag, The Netherlands, 16 - 21 Sept. 2007. Book of Extended Abstracts. Klein, C.R. (Ed.). Delft University of Technology (2007), 11. Invited talk.
Slides of invited talk on ALD for MEMS at the AVS-ALD conference ALD 2009 Monterey, California, USA
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Full reference:
R. L. Puurunen, M. Blomberg, H. Kattelus, ALD layer in MEMS fabrication, 9th International Conference on Atomic Layer Deposition “ALD 2009”, Monterey, California, July 19-22, 2009. Invited talk.
History of ald riikka puurunen 15.11.2013 finalRiikka Puurunen
Invited seminar talk by R. L. Puurunen, November 15, 2013, Beneq and ETU (LETI) joint ALD laboratory opening seminar, St. Petersburg, Russia, title: History of ALD: from lab research to industrial applications
Vapor Deposition of Semiconducting Phosphorus Allotropes into TiO2 Nanotube A...Pawan Kumar
Recent evidence of exponential environmental degradation will demand a drastic shift in research and development toward exploiting alternative energy resources such as solar energy. Here, we report the successful low-cost and easily accessible synthesis of hybrid semiconductor@TiO2 nanotube photocatalysts. In order to realize its maximum potential in harvesting photons in the visible-light range, TiO2 nanotubes have been loaded with earth-abundant, low-band-gap fibrous red and black phosphorus (P). Scanning electron microscopy– and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron microscopy, and UV–vis measurements have been performed, substantiating the deposition of fibrous red and black P on top and inside the cavities of 100-μm-long electrochemically fabricated nanotubes. The nanotubular morphology of titania and a vapor-transport technique are utilized to form heterojunctions of P and TiO2. Compared to pristine anatase 3.2 eV TiO2 nanotubes, the creation of heterojunctions in the hybrid material resulted in 1.5–2.1 eV photoelectrocatalysts. An enhanced photoelectrochemical water-splitting performance under visible light compared with the individual components resulted for the P@TiO2 hybrids. This feature is due to synergistically improved charge separation in the heterojunction and more effective visible-light absorption. The electronic band structure and charge-carrier dynamics are investigated in detail using ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy to elucidate the charge-separation mechanism. A Fermi-level alignment in P@TiO2 heterojunctions leads to a more reductive flat-band potential and a deeper valence band compared to pristine P and thus facilitates a better water-splitting performance. Our results demonstrate effective conversion efficiencies for the nanostructured hybrids, which may enable future applications in optoelectronic applications such as photodetectors, photovoltaics, photoelectrochemical catalysts, and sensors.
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Slides of an invited talk, given at EuroCVD in 2007
R. L. Puurunen, Understanding the surface chemistry of atomic layer deposition: achievements and challenges, Sixteenth European Conference on Chemical Vapor Deposition, EuroCVD-16. Den Haag, The Netherlands, 16 - 21 Sept. 2007. Book of Extended Abstracts. Klein, C.R. (Ed.). Delft University of Technology (2007), 11. Invited talk.
Slides of invited talk on ALD for MEMS at the AVS-ALD conference ALD 2009 Monterey, California, USA
---
Full reference:
R. L. Puurunen, M. Blomberg, H. Kattelus, ALD layer in MEMS fabrication, 9th International Conference on Atomic Layer Deposition “ALD 2009”, Monterey, California, July 19-22, 2009. Invited talk.
History of ald riikka puurunen 15.11.2013 finalRiikka Puurunen
Invited seminar talk by R. L. Puurunen, November 15, 2013, Beneq and ETU (LETI) joint ALD laboratory opening seminar, St. Petersburg, Russia, title: History of ALD: from lab research to industrial applications
Vapor Deposition of Semiconducting Phosphorus Allotropes into TiO2 Nanotube A...Pawan Kumar
Recent evidence of exponential environmental degradation will demand a drastic shift in research and development toward exploiting alternative energy resources such as solar energy. Here, we report the successful low-cost and easily accessible synthesis of hybrid semiconductor@TiO2 nanotube photocatalysts. In order to realize its maximum potential in harvesting photons in the visible-light range, TiO2 nanotubes have been loaded with earth-abundant, low-band-gap fibrous red and black phosphorus (P). Scanning electron microscopy– and scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron microscopy, and UV–vis measurements have been performed, substantiating the deposition of fibrous red and black P on top and inside the cavities of 100-μm-long electrochemically fabricated nanotubes. The nanotubular morphology of titania and a vapor-transport technique are utilized to form heterojunctions of P and TiO2. Compared to pristine anatase 3.2 eV TiO2 nanotubes, the creation of heterojunctions in the hybrid material resulted in 1.5–2.1 eV photoelectrocatalysts. An enhanced photoelectrochemical water-splitting performance under visible light compared with the individual components resulted for the P@TiO2 hybrids. This feature is due to synergistically improved charge separation in the heterojunction and more effective visible-light absorption. The electronic band structure and charge-carrier dynamics are investigated in detail using ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy to elucidate the charge-separation mechanism. A Fermi-level alignment in P@TiO2 heterojunctions leads to a more reductive flat-band potential and a deeper valence band compared to pristine P and thus facilitates a better water-splitting performance. Our results demonstrate effective conversion efficiencies for the nanostructured hybrids, which may enable future applications in optoelectronic applications such as photodetectors, photovoltaics, photoelectrochemical catalysts, and sensors.
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
Bespoke compositions and microstructures from suspension and solution precurs...Tanvir Hussain
Presentations by Dr Hussain at the TS4+E conference in Montreal. Canada 17-18 Sep 2019, Thermal Spraying of Suspensions and solutions symposium + environmental barrier coatings
Invited talk at 98th CSC: Surface chemistry of ALD: mechanisms and conformality Riikka Puurunen
Abstract of the presentation:
Atomic layer deposition (ALD) is a thin film growth method generally applicable for the growth of conformal, highquality
inorganic material layers down to the nanometer thickness range. ALD is indifferent to the morphology of the
underlying substrate and covers even most complex 3-D shapes with a uniform film; as a consequence, ALD is used
in an ever-increasing field of applications from catalysts to photovoltaics to microelectronics and beyond. ALD
belongs to the general class of chemical vapour deposition (CVD) techniques. The speciality of ALD is the use of
repeated self-terminating (saturating, irreversible) gassolid reactions of at least two reactants for the film growth; ALD
is therefore non-continuous in nature, as opposed to the continuous CVD processes. In this presentation, I will
discuss some challenges related to understanding the surface chemistry of ALD. The commonly-used
trimethylaluminium-water ALD process to deposit Al2O3 is used as case example, as it is often presented as model
case for ALD. I will also discuss the characteristics of ALD film conformality, as detected by using microscopic lateral
high-aspect-ratio structures ("VTT μLHAR") [J. Vac. Sci. Technol. A 33, 010601 (2015)]. Here, the gap height is in
the range of 100 nm's and the aspect ratio (AR) can be extremely challenging, e.g. up to 25 000:1. Finally, I will
briefly introduce the on-going international volunteer-based Virtual Project on the History of ALD (http://vph-ald.com),
where new participants are still welcome.
Acknowledgement: The author thanks Finnish Centre of Excellence in Atomic Layer Deposition for funding.
Shulze - Surface and Thin Film Characterization of Superconducting Multilayer...thinfilmsworkshop
http://www.surfacetreatments.it/thinfilms
Surface and Thin Film Characterization of Superconducting Multilayer films for application in RF (Roland Schulze - 30')
Speaker: Roland Schulze - Los Alamos National Laboratory | Duration: 30 min.
Abstract
The use of multilayer ultra-thin films on the interior surfaces of Nb superconducting RF cavities shows great promise in substantially improving the performance characteristics of superconducting RF cavities into the 100 MV/m range by increasing the RF critical magnetic field, HRF, through careful choice of new materials and thin film structures. However, there are substantial materials science challenges associated with producing such complex film structures, particularly for conformal application of uniform thin films on the interior surfaces of RF cavities. Here we present surface and thin film analysis of ultra-thin films of two candidate materials, MgB2 and NbN superconductors, deposited through several different methods, along with multilayers produced with alternating superconductor and dielectric films. We report on the analysis methods and techniques, using primarily x-ray photoelectron spectroscopy and Auger spectroscopy with ion sputter depth profiling, and describe results from variety of thin film samples. The materials stability, microstructure, chemistry, and thin film morphology are highly dependent on methods and parameters used in the thin film deposition. From our analysis, important factors for producing quality superconducting and dielectric films include chemical stoichiometry, impurity content, deposition temperature, substrate choice and conditioning, choice of dielectric material, and the nature of the thin film interfaces. These factors will be discussed in the context of the production methods used for these ultra-thin superconducting films.
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
Bespoke compositions and microstructures from suspension and solution precurs...Tanvir Hussain
Presentations by Dr Hussain at the TS4+E conference in Montreal. Canada 17-18 Sep 2019, Thermal Spraying of Suspensions and solutions symposium + environmental barrier coatings
Invited talk at 98th CSC: Surface chemistry of ALD: mechanisms and conformality Riikka Puurunen
Abstract of the presentation:
Atomic layer deposition (ALD) is a thin film growth method generally applicable for the growth of conformal, highquality
inorganic material layers down to the nanometer thickness range. ALD is indifferent to the morphology of the
underlying substrate and covers even most complex 3-D shapes with a uniform film; as a consequence, ALD is used
in an ever-increasing field of applications from catalysts to photovoltaics to microelectronics and beyond. ALD
belongs to the general class of chemical vapour deposition (CVD) techniques. The speciality of ALD is the use of
repeated self-terminating (saturating, irreversible) gassolid reactions of at least two reactants for the film growth; ALD
is therefore non-continuous in nature, as opposed to the continuous CVD processes. In this presentation, I will
discuss some challenges related to understanding the surface chemistry of ALD. The commonly-used
trimethylaluminium-water ALD process to deposit Al2O3 is used as case example, as it is often presented as model
case for ALD. I will also discuss the characteristics of ALD film conformality, as detected by using microscopic lateral
high-aspect-ratio structures ("VTT μLHAR") [J. Vac. Sci. Technol. A 33, 010601 (2015)]. Here, the gap height is in
the range of 100 nm's and the aspect ratio (AR) can be extremely challenging, e.g. up to 25 000:1. Finally, I will
briefly introduce the on-going international volunteer-based Virtual Project on the History of ALD (http://vph-ald.com),
where new participants are still welcome.
Acknowledgement: The author thanks Finnish Centre of Excellence in Atomic Layer Deposition for funding.
Shulze - Surface and Thin Film Characterization of Superconducting Multilayer...thinfilmsworkshop
http://www.surfacetreatments.it/thinfilms
Surface and Thin Film Characterization of Superconducting Multilayer films for application in RF (Roland Schulze - 30')
Speaker: Roland Schulze - Los Alamos National Laboratory | Duration: 30 min.
Abstract
The use of multilayer ultra-thin films on the interior surfaces of Nb superconducting RF cavities shows great promise in substantially improving the performance characteristics of superconducting RF cavities into the 100 MV/m range by increasing the RF critical magnetic field, HRF, through careful choice of new materials and thin film structures. However, there are substantial materials science challenges associated with producing such complex film structures, particularly for conformal application of uniform thin films on the interior surfaces of RF cavities. Here we present surface and thin film analysis of ultra-thin films of two candidate materials, MgB2 and NbN superconductors, deposited through several different methods, along with multilayers produced with alternating superconductor and dielectric films. We report on the analysis methods and techniques, using primarily x-ray photoelectron spectroscopy and Auger spectroscopy with ion sputter depth profiling, and describe results from variety of thin film samples. The materials stability, microstructure, chemistry, and thin film morphology are highly dependent on methods and parameters used in the thin film deposition. From our analysis, important factors for producing quality superconducting and dielectric films include chemical stoichiometry, impurity content, deposition temperature, substrate choice and conditioning, choice of dielectric material, and the nature of the thin film interfaces. These factors will be discussed in the context of the production methods used for these ultra-thin superconducting films.
Igneous rocks formaion through chemical weatheringrita martin
Igneous rocks are generally termed as fire rocks formed either underground or above ground there are two types Intrusive, Extrusive igneous rocks mainly containing high silica content
surface characteristics and electrochemical impedance investigation of spark-...mohammad fazel
In this study, the surface characteristic of oxide films on Ti-6Al-4V alloy formed by an anodic oxidation treatment at potentials higher than the breakdown voltage was evaluated.
This lecture describes the key factors associated with conversion coatings on aluminium can be appreciated, such as general and local behaviour of the aluminium surface, range of conversion coatings and interrelationships, requirements of conversion coating, tailor-making of coatings, current and future issues. Some familiarity with the subject matter covered in TALAT This lectures 5101, 5102, 5201 is assumed.
NATURAL CONVECTIVE HEAT TRANSFER BY Al2O3 &PbO NANOFLUIDSAlagappapandian M
In this presentation related about natural convective heat transfer incresed by using different nano particles. in this fluid is called nanofluids. Nanofluids improve the heat transfer rate of base fluid.
TripleHard - Trivalent Based Hard Chrome - Case TecnocromSavroc Ltd
A case example of integration of TripleHard trivalent based hard chromium coating technology into Tecnocrom Industrial's existing electroless nickel plating line. TripleHard allows cost-efficient manufacturing of hard and wear-resistant coatings for demanding conditions without the carcinogenic chromic acid used in traditional hexavalent based hard chromium.
Read more information and contact Savroc to get a license to use TripleHard method at: www.savroc.com
40 cfr 261.4(b)(6) The RCRA Exclusion From Hazardous Waste for Trivalent Chro...Daniels Training Services
The Trivalent Chromium Wastes Exclusion from Regulation as a Hazardous Waste
40 CFR 261.4(b)(6) excludes Trivalent Chromium Waste, a solid waste, from regulation as a hazardous waste if the requirements of the regulations are met. This presentation briefly summarizes the requirements of this RCRA exclusion from regulation.
Those in the leather tanning industry, leather product manufacturing industry, shoe manufacturing industry, and titanium dioxide manufacturing industry should be aware of this RCRA exclusion and its possible impact on their operations.
Chromium is a metal that exists in several oxidation
• Chromium is a metal that exists in several oxidation or valence states, ranging from chromium (-II) to chromium (+VI).
• Chromium compounds are very stable in the trivalent state and occur naturally in this state in ores such as ferrochromite, or chromite ore.
• Chrome III is an essential nutrient for maintaining blood glucose levels
• The hexavalent, Cr(VI) or chromate, is the second most stable state. It rarely occurs naturally.
A SHORT REVIEW ON ALUMINIUM ANODIZING: AN ECO-FRIENDLY METAL FINISHING PROCESSJournal For Research
Protection of aluminium alloys is most commonly done by forming anodic films. Anodic films can also be formed on metals like titanium, zinc, magnesium, niobium, and tantalum. Aluminium alloy parts are anodized to greatly increase the thickness of the natural oxide layer for corrosion resistance. A thin aluminium oxide film, that seals the aluminium from further oxidation when it is exposed to air. The anodizing process increases the thickness of the oxidized surface. Anodizing is accomplished by immersing the aluminium into an acid electrolyte bath and passing an electric current through the medium. In an anodizing cell, the aluminium work piece is made the anode by connecting it to the positive terminal of a dc power supply and the cathode is connected to the negative terminal of the dc source. Sealing is needed to seal the pores in oxide layer to prevent further corrosion. Oxide layer on the anodized aluminium has a highly ordered, porous structure that allows for secondary processes such as dyeing, printing and sealing. Nanowires and nanotubes can be made by using the pores in the oxide layer as templates.
Improving Mechanical Properties of AL 7075 alloy by Equal Channel Angular Ext...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Effect of cold rolling on low cycle fatigue behavior eSAT Journals
Abstract Four cold reductions, viz. 2.5, 5, 7.5 and 10 percent are given to a near- Titanium alloy Timetal 834, following solution treatment in α+β range and stabilization. LCF tests were conducted at room temperature in total strain control mode at Δεt/2 from 0.45% to 1.05%. Prior to LCF testing, gage section of the specimens was elecrtopolished to reveal the surface modifications, resulting from fatigue testing. It was observed that cold rolling considerably enhanced fatigue life of the alloy. Key words: Titanium alloys; cold rolling; low-cycle fatigue; strain rate; Coffin-Manson relation
Synthesis and Characterization Studies of Solvothermally Synthesized Undoped ...IJERA Editor
Nanocrystalline TiO2 was investigated by solvothermal synthetic method using toluene as a solvent. Titanium tetra isopropoxide (TTIP) was used as a precursor, which was decomposed at high temperature and precipitated in toluene. Subsequently, the solution was thermally treated at 250C for five hours in stainless steel autoclave. Amorphous Nano TiO2 was formed. When these amorphous Nano TiO2 was calcinated to 550 C anatase Nano TiO2 crystalline with particle size <20 nm was formed. These amorphous and anatase phase Nano TiO2 was characterized by Powder X-ray diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and Photoluminescence (PL) studies and the results were discussed.
A lecture on the use of in-situ synchrotron tomographic imaging for studying the microstructure of silicate glasses and melts.
Course given at the summer school "Du verre au liquide".
Plenary lecture of the XIII SBPMat (Brazilian MRS) meeting, given on September 30th 2014 by Karl Leo, professor of optoelectronics at Dresden University of Technology (Germany) and director of the Solar and Photovoltaic Engineering Research Center at KAUST (Saudi Arabia).
Invited talk by R.L. Puurunen "Recent Progress in Analysis of the Conformality of Films by Atomic Layer Deposition" at AVS69, Portland, Oregon, Nov 5-10, 2023, https://avs69.avs.org/.
ABSTRACT. Conformality is a fundamental characteristic of atomic layer deposition (ALD) thin film growth technique. “Conformal” film refers to a film that covers all surfaces of a complex three-dimensional substrate with everywhere the same thickness and properties. ALD - invented independently by two groups in 1960s and 1970s - has since late 1990s been transformational in semiconductor technology. Apart from semiconductors, conformal ALD films find applications and interest in widely varied fields such as microelectromechanical systems, pharmaceutical powder processing, optical coatings, battery technologies and heterogeneous catalysts.
Conformality follows directly from the “ideal ALD” principles: growth of material through the use of repeated separate self-terminating (i.e., saturating and irreversible) gas-solid reactions of at least two compatible reactants on a solid surface. Obtaining conformality in practice is not self-evident, however. Reasons for deviation from conformality are multiple, ranging from mass transport limitations to slow reaction kinetics and various deviations from ideal ALD (e.g., by-product reactivity or a continuous chemical vapor deposition (CVD) component through reactant decomposition or insufficient purging). Incomplete conformality can also be intentional: a saturation profile inside a feature can be exposed, to enable an analysis of kinetic parameters of the reactions.
This invited talk will explore recent progress especially by the author and collaborators in understanding ALD conformality and kinetics, obtained via experiments and simulations. Experiments have been made with the recently commercialized (chipmetrics.com) silicon-based PillarHallTM lateral HAR test chips (channel height ~500 nm) and spherical mesoporous high-surface-area materials (average pore diameter ~10 nm, sphere diameter ~1 mm). Simulations are presented for 1d feature-scale models and optionally a recently developed 3d code for spheres. Two codes are available on GitHub: DReaM-ALD (diffusion-reaction model, DRM) and Machball (ballistic transport-reaction model, BTRM). Often it is assumed that diffusion during an ALD process in HAR features is by Knudsen diffusion and free molecular flow conditions prevail (Kn >>1). If so, a characteristic “fingerprint saturation profile” can be obtained, and the slope method (derived for DRM-ALD-Arts, GitHub) can be used to back-extract the lumped sticking coefficient. When diffusion is in the transition flow (Kn ~1) or continuum flow (Kn<<1), the shape of the saturation profile depends on process conditions and the slope method is not applicable.
Puurunen (on behalf of Järvilehto) oral presentation at ALD 2023 conferenceRiikka Puurunen
ALD 2023, Bellevue, Washington, July 2023
AUDIO: (see 1st page)
Title: Simulated Conformality of ALD Growth Inside Lateral HAR Channels: Comparison Between a Diffusion–Reaction Model and a Ballistic Transport–Reaction Model
Authors: Jänis Järvilehto,1 Jorge A. Velasco,1 Jihong Yim,1 Christine Gonsalves1 and Riikka L. Puurunen1
1Aalto University, School of Chemical Engineering, Department of Chemical and Metallurgical Engineering
Atomic layer deposition (ALD) is known for its ability to produce films of controllable thickness, even in narrow, high-aspect-ratio (HAR) structures [1]. These films can be highly conformal, meaning that the structure is covered by a film of uniform thickness [1,2]. However, when the structure’s aspect ratio is increased sufficiently, deposition becomes limited by the diffusion of the reactants into the deep end of the structure, potentially resulting in the formation of an adsorption front, followed by a region of lower coverage [3]. Theoretical models have been developed to predict film conformality in HAR structures, as reviewed in [2].
This work presents a comparison of a diffusion–reaction model (DRM) developed by Ylilammi et al. [4,5] (Model A) and a ballistic transport–reaction model (BTRM) by Yanguas-Gil and Elam [6,7] (Model B). For the comparison, saturation profiles were generated using both models with similar simulation parameters (Knudsen number Kn >> 1).
Qualitatively, both models produced similar trends in terms of half-coverage penetration depth and slope at half-coverage penetration depth. The saturation profiles were similar in shape, except for the film growth observed at the channel end in Model B. Quantitative examination yielded consistently higher half-coverage penetration depths in Model B. Model A produced steeper slopes at half-coverage penetration depth. In Model B, the discretization resolution was found to affect the penetration depth.
While the models gave qualitatively similar results, quantitatively extracted parameters differed. This finding is consistent with a previous comparison of a DRM and BTRM in the context of low pressure chemical vapor deposition [8]. The quantitative differences are relevant, for example, when the models are fitted to experimental data for the extraction of kinetic parameters, such as the sticking coefficient.
[1] J.R. van Ommen, A. Goulas, and R.L. Puurunen, “Atomic layer deposition,” in Kirk Othmer Encyclopedia of
Chemical Technology, John Wiley & Sons, Inc., 42 p, (2021).
[2] V. Cremers et al., Appl. Phys. Rev. 6 (2019) 021302.
[3] J. Yim and O.M.E. Ylivaara et al., Phys. Chem. Chem. Phys. 22 (2020) 23107-23120.
[4] M. Ylilammi et al., J. Appl. Phys. 123 (2018) 205301.
[5] J. Yim and E. Verkama et al., Phys. Chem. Chem. Phys. 24 (2022) 8645–8660.
[6] A. Yanguas-Gil and J.W. Elam, Theor. Chem. Acc. 133 (2014) 1465.
[7] A. Yanguas-Gil and J.W. Elam, (2013) ...
Puurunen invited talk at IUPAC|Chains2023, The Hague, Netherlands, Aug 20-25,...Riikka Puurunen
Title: Atomic layer deposition: Introduction and progress examples
RECORDED AUDIO: https://aalto.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=835b50be-f687-463a-b0dc-b06900e0b47b
IUPAC|CHAINS2023 August 20-25, 2023. ‘Connecting Chemical Worlds’
Invited talk in parallel session 62: Advanced Thin Film Technology of Energy and Smart Materials
ABSTRACT
Atomic layer deposition (ALD), a thin film growth method based on self-terminating gas-solid reactions, has enabled the miniaturization of semiconductor devices in 2000s and finds commercial and emerging applications in varied other fields [1]. ALD has been invented independently twice [2,3]; in 1998, the Finnish inventor of ALD Tuomo Suntola received the Millennium Technology Prize for his pioneering work. This invited talk will first introduce the chemical principles of ALD. The ideally self-terminating (saturating, irreversible) reactions lead to almost unparalleled uniformity and conformality of the films, and to expanding interest in the ALD technique. Second, case examples will be shared of recent research in Puurunen’s group at Aalto University related to preparation of heterogeneous catalysts by ALD and conformality investigations by experiments and modelling. As the speaker is interested in bringing more openness to science and education in a sustainable way, recent progress in Open Science in the field of ALD will be also briefly touched upon.
References:
[1] J.R. van Ommen, A. Goulas, R.L. Puurunen, “Atomic layer deposition”, in Kirk-Othmer Encyclopedia of Chemical Technology, 2021, https://doi.org/10.1002/0471238961.koe00059.
[2] R.L. Puurunen, “A Short History of Atomic Layer Deposition: Tuomo Suntola's Atomic Layer Epitaxy”, Chem. Vap. Deposition 20 (2014) 332-344. https://doi.org/10.1002/cvde.201402012
[3] A.A. Malygin, V.E. Drozd, A.A. Malkov, V.M. Smirnov, “From V. B. Aleskovskii's “Framework” Hypothesis to the Method of Molecular Layering/Atomic Layer Deposition”, Chem. Vap. Deposition 21 (2015) 216-240. https://doi.org/10.1002/cvde.201502013
Slides of invited "ALD 101" tutorial by Puurunen at ALD 2021 Riikka Puurunen
(INVITED) Fundamentals of atomic layer deposition: an introduction (“ALD 101”)
Riikka L. Puurunen, Aalto University School of Chemical Engineering, Department of Chemical and Metallurgical Engineering, AVS 21st International Conference on Atomic Layer Deposition (ALD 2021), Virtual Meeting 27.6.-30.6.2021. Tutorial Session 27.6.2021
ABSTRACT: Atomic layer deposition (ALD) has become of global importance as a processing technology for example in semiconductor device fabrication, and its application areas are continuously expanding. The significance of ALD was highlighted e.g. by the recent (2018) Millennium Technology Prize. Tens of companies are offering ALD tools, and thousands of people are involved in ALD R&D globally. A continuous need exists to educate new people on the fundamentals of ALD.
While ALD for manufacturing may be regarded mature, as a scientific field, ALD—in the author’s view—is developing. For example, understanding of the early history of ALD is evolving, related to the two independent inventions of ALD under the names Atomic Layer Epitaxy in the 1970s and Molecular Layering in the 1960s [1-4]. Also, significantly varying views exist in the field related to the description and meaningfulness of even some core ALD concepts [5].
The purpose of this invited “ALD 101” tutorial is to familiarize a newcomer with fundamentals of ALD. The presentation largely follows the organization of a recent encyclopedia chapter on ALD [6]. Surface chemistry concepts will be introduced, such as ideal ALD from repeated, separate self-terminating (saturating and irreversible) reactions; growth per cycle in ALD; various monolayer concepts relevant to ALD; typical classes of surface reaction mechanisms and saturation-determining factors; growth modes; and ways to describe growth kinetics. Concepts, where differing views exist in the field and which thus need special attention, are pointed out. Typical deviations from the presented ideality are discussed.
For continuous education, a collaborative OpenLearning website on ALD is under construction [7]. Many of the images used in this tutorial—and in Refs. 6 and 7—are available in Wikimedia Commons [8] for easy and free reuse. To contribute to collective learning of the early history of ALD, the open-science effort Virtual Project on the History of ALD [4] still welcomes new volunteer participants.
[1] E. Ahvenniemi et al., J. Vac. Sci. Technol. A 35 (2017) 010801 (2017).[2] R.L. Puurunen, ECS Transactions 86 (6) (2018) 3-17; OA: DOI:10.1149/osf.io/exyv3[3] G.N. Parsons et al., J. Vac. Sci. Technol. A 38 (2020) 037001.[4] http://vph-ald.com[5] J.R. van Ommen, R.L. Puurunen, ALD 2020, https://youtu.be/jqm_wf49WwM[6] J.R. van Ommen, A. Goulas, R.L. Puurunen, Kirk-Othmer Encyclopedia on Chemical Technology, submitted. [7] http://openlearning.aalto.fi, ALD [8] https://commons.wikimedia.org/wiki/Category:Atomic_layer_deposition
"On the fundamentals of ALD: the importance of getting the picture right" by ...Riikka Puurunen
Presentation at the AVS 20th International Conference on Atomic Layer Deposition (ALD 2020) featuring the 7th International Atomic Layer Etching Workshop (ALE 2020), online, 29.6.-1.7.2020.
Authors: Riikka L. Puurunen and J. Ruud van Ommen
Abstract text:
Atomic layer deposition (ALD) has become of global importance as a fundamental building block for example in semiconductor device fabrication, and also gained more visibility (e.g., the Millennium Technology Prize 2018). In recent years, the number of ALD processes has increased, new groups have entered the field, and fundamental insights have been gained. At the same time, significantly varying views exist in the field related to the description and meaningfulness of some core ALD concepts. Open, respectful but critical scientific discussion would be needed around these concepts - for example at this AVS ALD/ALE conference, the world’s largest conference on ALD.
The discussion on terminology of ALD that started in the 2005 surface chemistry review [1] is continued in this contribution, taking into account recent progress reported in leading reviews such as Ref. 2. We start by considering the concept of “ideal ALD”. How should it be defined so that the well-recognized practical benefits of ALD are maintained, while no unnecessary utopian requirements are created? We propose that the repetition of well-separated saturating, irreversible chemisorption reactions (which by definition saturate at a monolayer of the chemisorbed species) is sufficient to reproduce the benefits of ALD. A requirement of “full monolayer growth” (of the ALD-grown material), progressed e.g. in numerous cartoons of ALD, is not needed. There should also be no reason to expect a constant growth per cycle (GPC) within the ALD window (the saturating chemistry is typically weakly temperature dependent), although such a scheme is repeatedly reproduced in the literature.
Other fundamental concepts will be pointed out, where mix-ups have been created. For example, although the GPC (or etch per cycle in Atomic Layer Etching) is a saturation-related concept and not a time-related kinetic parameter, Arrhenius plots have been sometimes created to extract “activation energies” of some process from these “growth/etch rates (per cycle)”. Also, “Langmuir adsorption” has been adopted as a way to model ALD in a simplified, lumped way. Notably, Langmuir adsorption assumes no interaction between adsorbed species, contrasting some recent discussions of “cooperative effects” in ALD. Also, concepts of “adsorption isotherm” and amount adsorbed vs. time (“saturation curve”), although fundamentally different, have been mixed.
We hope that the discussion on the fundamentals of ALD will be intensified, and that the discussion will help the field progress and flourish in the future.
[1] Puurunen, J. Appl. Phys. 97 (2005) 121301.
[2] Richey, de Paula, Bent, J. Chem. Phys. 152 (2020) 040902.
Catalysis Connected, Utrecht - slides of invited talk by Prof. Riikka PuurunenRiikka Puurunen
Talk given in Utrecht, The Netherlands, August 24, 2019
Title: Atomic layer deposition: Bridging semiconductors to catalysis and beyond
Abstract: This talk will briefly explain the fundamentals of atomic layer deposition (ALD), view key historical turning points of the technique, and attempt to look into the future of ALD in the field of catalysis. ALD, a thin film growth method based on repeated self-terminating gas-solid reactions of compatible compounds, has become known as an enabler of Moore’s law and is today commonplace in the manufacturing of semiconductor devices. Currently, ALD is seen as highly promising for the controlled preparation of heterogeneous catalysts, testified e.g. from the number of reviews that appear on the topic. ALD can be used to grow films or nanoparticles and even single sites, and it can be similarly applied on powders, engineered 3D structures, and flat model catalysts.
Surface coverage in atomic layer deposition - slides related to invited talk ...Riikka Puurunen
Invited talk given at the Workshop on Fundamentals of Atomic Layer Deposition (ALD): Modelling and ValidationTU Delft, The Netherlands, July 3, 2019. Talk was recorded by TU Delft staff and is to be shared later. Website: https://www.tudelft.nl/en/faculty-of-applied-sciences/about-faculty/departments/chemical-engineering/scientific-staff/van-ommen-group/workshop-fundamentals-of-ald/. Twitter hashtag: #ALDfun
ALD for Industry 2019: Slides of invited tutorial by Prof. Riikka PuurunenRiikka Puurunen
Invited tutorial given by Prof. Riikka Puurunen at the ALD for Industry event, Berlin, 19.3.2019.
Video record taken with Panopto, (to be) shared in Youtube, you find the links e.g. through the blog post: https://blogs.aalto.fi/catprofopen/2019/03/19/prof-puurunen-invited-tutorial-at-ald-for-industry-berlin/
Title: ALD Technology – Introduction, History & Principles
Abstract: This tutorial keynote will introduce atomic layer deposition (ALD) – a variant of chemical vapor deposition - and fundamental principles and concepts related it from a generic viewpoint applicable to any ALD process and reactor. The early history and current usage of ALD are briefly overviewed: who made the first experiments, when, and why? How has the view on the history of ALD evolved? Where is ALD now used, by whom, and why? ALD relies on repeated chemical adsorption steps from gas phase to surface. The status of understanding the adsorption steps of ALD films will be presented and discussed using mainly the archetype trimethylaluminium-water ALD process as example and 3D conformality modelling as additional vehicle. Plenty of links to further sources of information will be included in this keynote presentation.
A related SlideShare: placeholder, where I meant to update the slides afterwards, but this did not succeed as the reupload function has been removed: https://www.slideshare.net/RiikkaPuurunen/ald-for-industry-2019-invited-tutorial-by-prof-riikka-puurunen/RiikkaPuurunen/ald-for-industry-2019-invited-tutorial-by-prof-riikka-puurunen. The update was waiting for the publication of the following review article, which was still in press when giving the presentation: Cremers, Puurunen, Dendooven, Appl. Phys. Rev. (2019), https://doi.org/10.1063/1.5060967. Article published 4.4.2019: Applied Physics Reviews 6, 021302 (2019)
ALD for Industry 2019: Invited tutorial by Prof. Riikka Puurunen Riikka Puurunen
Oops! Could not update this placeholder with the final presentation as planned: The reupload function that I planned to use, has been removed from SlideShare, see: https://www.slideshare.net/dolaneconslide/bring-back-reupload
Slides uploaded separately: https://www.slideshare.net/RiikkaPuurunen/ald-for-industry-2019-slides-of-invited-tutorial-by-prof-riikka-puurunen
Originally, this update was waiting for the publication of a review article to be published on ALD conformality: Cremers, Puurunen, Dendooven, Appl. Phys. Rev. (2019), https://doi.org/10.1063/1.5060967. Article published 4.4.2019: Applied Physics Reviews 6, 021302 (2019)
Related post in Catalysis Professor's Open: https://blogs.aalto.fi/catprofopen/2019/03/19/prof-puurunen-invited-tutorial-at-ald-for-industry-berlin/
Adsorption-controlled catalyst preparation by ALDRiikka Puurunen
Lecture slides of Prof. Riikka Puurunen at Aalto University School of Chemical Engineering, CHEM-E1130 Catalysis, 25.2.2019, on the preparation of catalysts by atomic layer deposition.
Introduction to atomic layer deposition (ALD): principles, applications, futureRiikka Puurunen
<erratum at the bottom / update 3.5.2019> Introductory lecture on Atomic Layer Deposition (ALD) by Prof. Riikka Puurunen, given at Aalto University School of Chemical Engineering on November 8, 2018. Lecture contents: Principles and concepts of ALD; Some history; Applications of ALD; Words on future. In addition to the core lecture contents, discusses where we have ALD layers in our smart mobile phones; mentions (some) faces of ALD in Finland; STG podcasts; Virtual Project on the History of ALD.
Corresponding lecture capture by Panopto available at: https://aalto.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=bd0aee67-7ca5-4973-8216-a99200e888b1
Erratum! Small errors spotted in the slides are described below. Updated 3.5.2019.
* slide 44 Luminescent: ZnS:Mg —> not Mg but Mn! --> ZnS:Mn
* slide 54 high-k solution: article not from 2017 but 2007
On the history and future of ALD: VPHA, conformality analysis, mechanismsRiikka Puurunen
Invited presentation at the HERALD COST MP1402 event in Riga (Riika), Latvia, May 22-23, 2017.
Topics:
1) History of atomic layer deposition (ALD)
2) Conformality analysis of ALD and other thin films
3) Surface chemistry questions in ALD
Presentation dedicated to the memory of Mr. Sven Lindfors, pioneer in building ALD reactors, close collaborator of Dr. Tuomo Suntola from 1975.
ALD ATO nanolaminates with adjustable electrical properties, poster published...Riikka Puurunen
R. L. Puurunen, H. Kattelus, ALD ATO nanolaminates with adjustable electrical properties, 9th International Conference on Atomic Layer Deposition “ALD 2009”, Monterey, California, July 19-22, 2009. Poster presentation.
Acknowledgement (from the Abstract):
Acknowledgements: The authors are grateful to Ari Häärä for making the electrical measurements and to Sari Sirviö for supervising part of the sample fabrication and for initial interpretations of the results of the electrical measurements. This work was performed within the “ALDKOMP” project funded by Tekes (Finnish Funding Agency for Technology and Innovation).
Poster presented at the AVS ALD 2005 conference. This contains Al2O3 solubility data in deionized water and a report on the "bubbles" which form on ALD Al2O3 when heated. This work has been cited sometimes especially for the bubble formation, and now I want to make it easily accessible for all.
---
Controlling the Solubility of ALD Aluminium Oxide in Deionised Water
Riikka L. Puurunen, Jyrki Kiihamäki and Hannu Kattelus
VTT Technical Research Centre of Finland
Nucleophilic Addition of carbonyl compounds.pptxSSR02
Nucleophilic addition is the most important reaction of carbonyls. Not just aldehydes and ketones, but also carboxylic acid derivatives in general.
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Electronic effects (inductive effects, electron donation) have a large impact on reactivity.
Large groups adjacent to the carbonyl will slow the rate of reaction.
Neutral nucleophiles can also add to carbonyls, although their additions are generally slower and more reversible. Acid catalysis is sometimes employed to increase the rate of addition.
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Slides from talk:
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Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
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1. Atomic scale modeling of
atomic layer deposition processes
Riikka Puurunen
MEMS Technology Group
VTT Technical Research Centre of Finland
2. 2
Riikka Puurunen, 09 Aug 2005
ALD is fantastic !
Sneh et al.,
Thin Solid Films 402 (2002) 248.
Si Al2O3/Ta2O5 nanolaminate
Al2O3: 1.4 nm (~15 cycles)
Ta2O5: 2.7 nm
3. 3
Riikka Puurunen, 09 Aug 2005
But fantastic ≠ perfect
electrical performance of
field effect transistors
14
20 25
30,
40
down-scaling
successful
down-scaling fails
50
60
80
HfCl4/H2O
cycles
Down-scaling
stops — why?
figure courtesy Schram et al., IMEC
data Ragnarsson et al., VLSI2005, p. 234
turning point:
3-5 nm HfO2
4. 4
Riikka Puurunen, 09 Aug 2005
Many historical assumptions on ALD are invalid.
Atomic scale models help to understand why
temperature
mono-
layer
growth per cycle
cycles temperature cycles
growth per cycle
mono-
layer
5. 5
Riikka Puurunen, 09 Aug 2005
There are many types of atomic-scale models
Computationally demanding (high-
performance computers required)
Computationally easy (pen, paper,
pocket calculator needed)
So far at best semi-quantitatively
related to growth characteristics such
as growth per cycle
Target: model quantitatively related
to growth characteristics such as
growth per cycle
A restricted system calculated in
great detail
Relevant system chosen?
A well selected, simplified
phenomenon treated.
Simplifications reasonable?
Not accessible to everyoneAccessible to anyone
Based on solving the Schrödinger
equation highly sophisticated
Based on simple geometrical
assumptions crude
Ab initio models“Ball models”
discussed not discussed
6. 6
Riikka Puurunen, 09 Aug 2005
Outline
Introduction
Existing models
• Growth per cycle (GPC) models
• Growth mode models (random deposition, island growth)
• Other recent models
What is the use of the models?
• Case 1. Mechanism of Al2O3 ALD (GPC model)
• Case 2. Density of nanometer-thin HfO2 films (growth mode models)
Conclusion
7. 7
Riikka Puurunen, 09 Aug 2005
Growth per cycle (GPC):
characteristic parameter of an ALD process
Growth per cycle
• defined by the choice of process: reactants,
temperature, substrate
• reactor-independent
Mass
increment
Time
Aarik et al.,
Thin Solid Films 340, 110 (1999).
cycles
growth
per
cycle
Classification:
Puurunen and Vandervorst, J. Appl. Phys. 96, 7686 (2004).
8. 8
Riikka Puurunen, 09 Aug 2005
(2004), in press.
Growth per cycle (should be) highly reproducible
Al2O3 growth temperature (°C)
AlMe3/H2O
GPC by different groups
within ~10% excellent !
Al atoms
per cycle
[nm-2]
HfO2 growth temperature (°C)
HfCl4/H2O
Hf atoms
per cycle
[nm-2]
Puurunen, J. Appl. Phys. 97, 121301 (2005) - a review
sometimes, scatter (>100%) in
results of different groups.
origin of scatter ???
9. 9
Riikka Puurunen, 09 Aug 2005
“Ball models” for the growth per cycle
M
L
MLn L
Model 1
further description: Puurunen, J. Appl. Phys. 97, 121301 (2005) - a review
Model 2 Model 3
Ritala et al*, Morozov et al.
*Chem. Mater. 5, 1174
(1993)
Ylilammi
Thin Solid Films 279, 124
(1996)
Siimon and Aarik, Puurunen*
*Chem. Vap. Deposition 9, 249
(2003)
10. 10
Riikka Puurunen, 09 Aug 2005
Growth per cycle typically
small fraction of a monolayer (ML)
Growth per cycle
• typically ~5-50% of ML
• limited by:
Reactant A,
chemisorbed monolayer
ALD-grown material
number
of reactive
sites?
• Less than ML growth has
consequences to growth mode and
layer characteristics
steric
hindrance?
other
factors?
11. 11
Riikka Puurunen, 09 Aug 2005
Growth mode defines
how material gets arranged during growth
Two-
dimensional
growth (2d)
Random
deposition
(RD)
cycles
Island growth
(IG)
12. 12
Riikka Puurunen, 09 Aug 2005
Growth mode models:
“shower model” for random deposition
AlN coverage (monolayers)
Substrate surface fraction
2d
RD
Measured
(LEIS)
Deposition probability
=
growth per cycle (in ML)
Model: Puurunen, Chem. Vap. Deposition 10, 159 (2004).
Application example: Puurunen et al., J. Appl. Phys. 96, 4878 (2004).
Data: Puurunen et al.,
Chem. Mater. 14, 720
(2002).
13. 13
Riikka Puurunen, 09 Aug 2005
Growth mode models:
island growth model
b • Spherical islands in
square surface lattice
• Random deposition on
the islands
Cycles
Growth
per
cycle
Excel spreadsheet for playing with the parameters:
riikka.puurunen@vtt.fi
Model, application: Puurunen & Vandervorst, J. Appl. Phys. 96, 7686 (2004).
Phase I II III
14. 14
Riikka Puurunen, 09 Aug 2005
Island growth explains “S-type” growth curves
(substrate-inhibited growth, Type 2)
Al2O3
Si substrate
Si cap
AlMe3 / H2O at 300°C on H-terminated Si
Model, application: Puurunen & Vandervorst, J. Appl. Phys. 96, 7686 (2004).
Data: Puurunen et al., J. Appl. Phys. 96, 4878 (2004).
2 0 0
0
p [
1 0 05 00
Al atoms
deposited
[nm-2]
Cycles
0
1
0 5 10 15
Al2O3 coverage (monolayers)
Substratesurfacefraction
experiment (LEIS)
2d growth
random deposition
island growth
Al2O3 coverage [ML]
Substrate
surface
fraction
15. 15
Riikka Puurunen, 09 Aug 2005
Other recent models
Alam & Green
J. Appl. Phys. 94, 3403 (2003)
• Model to simulate especially
substrate-inhibited growth curves
of Type 2. Simulation in two parts.
• Follow-up discussion
J. Appl. Phys. 2004, 2005
Kim, Kim & Kang
J. Appl. Phys. 97, 093505 (2005)
• Model to calculate nonlinear
growth curves for multicomponent
thin films from data on binary films
• Similarities with the random
deposition model
Number of cycles
Hfcoverage,Hf/cm2
16. 16
Riikka Puurunen, 09 Aug 2005
Outline
Introduction
Existing models
• Growth per cycle (GPC) models
• Growth mode models (random deposition, island growth)
• Other recent models
What is the use of the models?
• Case 1. Mechanism of Al2O3 ALD (GPC)
• Case 2. Density of nanometer-thin HfO2 films (growth mode)
Conclusion
17. 17
Riikka Puurunen, 09 Aug 2005
Case 1. Mechanism of Al2O3 ALD:
from where does the growth per cycle originate?
Decrease in GPC caused by
→ change in reaction mechanism
with temperature?
→ change in number of reactive
sites with temperature?
?
bulk reaction:
2 AlMe3 + 3 H2O Al2O3 + 6 CH4
(2004), in press.
Al2O3 growth temperature [°C]
Al atoms
per cycle
[nm-2]
150 250 300200
6
4
2
0
further description: R. L. Puurunen, Appl. Surf. Sci. 245, 6 (2005).
see also: Puurunen, J. Appl. Phys. 97, 121301 (2005) - a review
Al atoms
adsorbed
[nm-2]
AlMe3 reaction temperature [°C]
18. 18
Riikka Puurunen, 09 Aug 2005
Case 1. Mechanism of Al2O3 ALD?
Effect of OH concentration on adsorbed species
Methyl
groups
adsorbed
[nm-2]
OH groups [nm-2]
• 5-6 nm-2 ~ constant
• theoretical maximum 7.2 nm-2 (Model 3)
self-termination by steric hindrance of
ligands
further description: R. L. Puurunen, Appl. Surf. Sci. 245, 6 (2005).
see also: Puurunen, J. Appl. Phys. 97, 121301 (2005) - a review
• Infrared: AlMe3 reacts with ~all OH
19. 19
Riikka Puurunen, 09 Aug 2005
Case 1. Mechanism of Al2O3 ALD?
Effect of OH concentration on growth per cycle
Mass balance:
[Me] = 3 [Al] – ∆ [OH]
⇒ [Al] = 1/3 [Me] + 1/3 ∆ [OH]
Al2O3 growth temperature [°C]
Al atoms
per cycle
[nm-2]
[Al] = 1.68 + 0.37 [OH]
200°C 9 OH nm-2
300°C 7 OH nm-2
further description: R. L. Puurunen, Appl. Surf. Sci. 245, 6 (2005).
see also: Puurunen, J. Appl. Phys. 97, 121301 (2005) - a review
Surface OH group concentration
on alumina or silica [nm-2]
Al atoms
adsorbed
[nm-2]
y = 1.68 + 0.37 x
20. 20
Riikka Puurunen, 09 Aug 2005
Case 2. Density of
nanometer-thin HfO2 films?
Density
(TEM-
RBS)
[g cm-3]
RBS thickness [nm]
10
6
2
86420
bulk
density
RBS thickness [nm]
Equivalent
oxide
thickness
[nm]
• Why the measured low
density is not reflected in
electrical properties of HfO2?
further description: Puurunen et al., Appl. Phys. Lett. 86, 073116 (2005).
21. 21
Riikka Puurunen, 09 Aug 2005
Case 2. Origin of TEM-RBS
thickness difference?
HfO2
substrate
mixed layer
HfO2
substrate
substrate
HfO2
substrate
HfO2
ρ analysis ≈ 0 nm
XPS << 0.6 nm
HfO2
substrate
Cl,H
OH OH OH OH
AFM ≈ 2 x 0.2 nm
this case ≈ 0 nm
substrate
HfO2
2 filling layers: ≈ 0.6 nm
TXRF ≈ 0.05 nm
• expected minimum TEM-RBS difference ≈ 1 nm
HfO2
glue
substrate
10 nm
Olivier Richard / IMEC
further description: Puurunen et al., Appl. Phys. Lett. 86, 073116 (2005).
22. 22
Riikka Puurunen, 09 Aug 2005
Case 2. Density of
nanometer-thin HfO2 films?
further description: Puurunen et al., Appl. Phys. Lett. 86, 073116 (2005).
10
8
6
4
2
0
Densityρ
obs
[gcm
-3
]
86420
HfO2 thickness h
RBS
[nm]
0.4
0.6
0.8
1.0
RBS thickness [nm]
Density
(TEM-
RBS)
[g cm-3]
Atomic-scale roughness
difference in TEM, RBS
“low density” always
measured for nanometer-thin
films
23. 23
Riikka Puurunen, 09 Aug 2005
Outline
Introduction
Existing models
• Growth per cycle (GPC) models
• Growth mode models (random deposition, island growth)
• Other recent models
What is the use of the models?
• Case 1. Mechanism of Al2O3 ALD (GPC)
• Case 2. Density of nanometer-thin HfO2 films (growth mode)
Conclusion
24. 24
Riikka Puurunen, 09 Aug 2005
ALD is fantastic ! But fantastic ≠ perfect
• Atomic-scale ball models help to correlate
growth characteristics with performance
• Few models exist
space for many more models!
• Always needed: carefully obtained and
reproducible experimental data Temperature
GPC
?
• Near future: correlate experiments with atomic scale models
(both “ball models” and ab initio models)
• Predicting the features of new ALD processes—future or
utopia?
M
L
L
25. 25
Riikka Puurunen, 09 Aug 2005
Thanks to:
• All coauthors
• Past and present colleagues on ALD
• (ASM) Microchemistry
• Fortum Oil and Gas ( Neste Oil)
• Helsinki University of Technology (HUT)
• Interuniversity Microelectronics Centre (IMEC)
• VTT Technical Research Centre of Finland
• Special thanks to
• Tom Schram, electrical data (IMEC)
• Olivier Richard, TEM figure (IMEC)
• Additional financing: TEKES, ALD 2005
RIIKKA PUURUNEN
Research Scientist, Dr.
MEMS Technology
email: riikka.puurunen@vtt.fi
VTT TECHNICAL RESEARCH CENTRE
OF FINLAND
VTT Information Technology
Visiting address: Micronova, Tietotie 3,
Espoo
P.O. Box 1208, FIN-02044 VTT, Finland
26. 26
Riikka Puurunen, 09 Aug 2005
Appendix 1: Some recent work on ALD modelling (1/2)
• Film growth model of atomic layer deposition for multicomponent thin films
Kim et al., J. Appl. Phys. 97, 093505 (2005).
• Hafnium oxide films by atomic layer deposition for high-κ gate dielectric applications: analysis of the
density of nanometer-thin films
Puurunen et al., Appl. Phys. Lett. 86, 073116 (2005).
• Correlation between the growth-per-cycle and the surface hydroxyl group concentration in the atomic
layer deposition of aluminium oxide from trimethylaluminium and water
Puurunen, Appl. Surf. Sci., 245, 6 (2005).
• Island growth as a growth mode in atomic layer deposition: a phenomenological model,
Puurunen and Vandervorst, J. Appl. Phys. 96, 7686 (2004).
• Island growth in the atomic layer deposition of zirconium oxide and aluminum oxide on hydrogen-
terminated silicon: growth mode modeling and transmission electron microscopy,
Puurunen et al., J. Appl. Phys. 96, 4878 (2004).
• Random deposition as a growth mode in atomic layer deposition,
Puurunen, Chem. Vap. Deposition 10, 159 (2004).
[Correction: Chem. Vap. Deposition 11, 234 (2005).]
• Analysis of hydroxyl group controlled atomic layer deposition of hafnium dioxide from hafnium
tetrachloride and water,
Puurunen, J. Appl. Phys. 95, 4777 (2004).
[Comment: Alam and Green, J. Appl. Phys. 98, 016101 (2005),
Reply: Puurunen, J. Appl. Phys. 98, 016102 (2005).]
27. 27
Riikka Puurunen, 09 Aug 2005
Appendix 1: Some recent work on ALD modelling (2/2)
• Growth per cycle in atomic layer deposition: real application examples of a theoretical model,
Puurunen, Chem. Vap. Deposition 9, 327 (2003).
• Growth per cycle in atomic layer deposition: a theoretical model,
Puurunen, Chem. Vap. Deposition 9, 249 (2003).
[Correction: Chem. Vap. Deposition 10, 124 (2004).]
• Mathematical description of atomic layer deposition and its application to the nucleation and growth of
HfO2 gate dielectric layers
Alam and Green, J. Appl. Phys. 94, 3403 (2003)
[Analysis and application of the model: Puurunen, J. Appl. Phys. 95, 4777 (2004),
Further discussion: J. Appl. Phys. 98, 016101 (2005); J. Appl. Phys. 98, 016102 (2005).]
28. 28
Riikka Puurunen, 09 Aug 2005
Appendix 2: Selected reviews on ALD (1/2)
• Surface chemistry of atomic layer deposition: a case study for the trimethylaluminum/water process,
Puurunen, J. Appl. Phys. 97, 121301 (2005).
• Formation of metal oxide particles in atomic layer deposition during the chemisorption of metal chlorides:
a review,
Puurunen, Chem. Vap. Deposition, 11, 79 (2005).
• Some recent developments in the MOCVD and ALD of high-k dielectric oxides,
Jones et al., J. Mater Chem. 14, 3101 (2004).
• Advanced electronic and optoelectronic materials by Atomic Layer Deposition: An overview with special
emphasis on recent progress in processing of high-k dielectrics and other oxide materials,
Niinistö et al., Phys. Stat. Solidi A 201, 1443 (2004).
• Atomic layer deposition of metal and nitride thin films: Current research efforts and applications for
semiconductor device processing,
Kim, J. Vac. Sci. Technol., B 21, 2231 (2003).
• Atomic layer deposition chemistry: Recent developments and future challenges,
Leskelä and Ritala, Angew. Chem. Int. Ed. 42, 5548 (2003).
29. 29
Riikka Puurunen, 09 Aug 2005
Appendix 2: Selected reviews on ALD (2/2)
• Atomic layer deposition,
Ritala and Leskelä, Handbook of Thin Film Materials, Vol. 1, Ed. H.S. Nalwa, Academic Press (San
Diego) 2002, pp. 103-159.
• Adsorption controlled preparation of heterogeneous catalysts,
Haukka et al., Stud. Surf. Sci. Catal. 120A, 715 (1999).
• The chemical basis of surface modification technology of silica and alumina by molecular layering
method,
Malygin et al., Stud. Surf. Sci. Catal. 99, 213 (1996).
• Surface chemistry for atomic layer growth,
George et al., J. Phys. Chem. 100, 13121 (1996).
• Atomic layer epitaxy,
Suntola, Handbook of Crystal Growth, Vol. 3, Ed. D. T. J. Hurle, Elsevier (Amsterdam) 1994, pp.
601-663.
• Atomic layer epitaxy,
Goodman and Pessa, J. Appl. Phys. 60, R65 (1986).