Atomic Layer Deposition Of Ruthenium Research Articles

Area-Selective Atomic Layer Deposition of Ruthenium via Reduction of Interfacial Oxidation

Area-Selective Atomic Layer Deposition of Ruthenium via Reduction of Interfacial Oxidation

Enhanced nucleation mechanism in ruthenium atomic layer deposition: Exploring surface termination and precursor ligand effects with RuCpEt(CO)2

Enhanced nucleation mechanism in ruthenium atomic layer deposition: Exploring surface termination and precursor ligand effects with RuCpEt(CO)2

The surface chemistry of the atomic layer deposition of ruthenium on aluminum and tantalum oxide surfaces

The surface chemistry of Ru atomic layer deposition (ALD) processes based on the use of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)ruthenium(III) (Ru(tmhd)3) and either molecular oxygen or atomic hydrogen on aluminum oxide films was characterized by a combination of surface-sensitive techniques. The thermal decomposition of the Ru metalorganic precursor was determined, by using a combination of reflection-absorption infrared spectroscopy (RAIRS), temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS), to start below 400 K and to take place in a stepwise fashion over a wide range of temperatures. Gas-phase products from this chemistry include 2,2,6,6-tetramethyl-3,5-heptanedione (the protonated ligand, Htmhd; in a TPD peak at 520 K), isobutene (540 K; indicating the fragmentation of the organic ligands), and other products from isomerization and/or aldol condensation (650 and 730 K). This chemistry is accompanied by the reduction of the Ru3+ ions in two stages, involving the loss of some of their ligands and their direct bonding to the substrate first (between 500 and 600 K) and a full reduction to a metallic state later on (600–700 K). ALD cycles using either molecular oxygen or atomic hydrogen resulted in the slow build-up of Ru on the surface, but the co-deposition of carbon could not be avoided, at least in the initial cycles, while the alumina surface was still exposed. With O2, the Ru atoms alternate between partially-oxidized (after the O2 exposures) and zero-valent (after the Ru(tmhd)3 doses) states, and some Ru loss in the form of the volatile RuO4 oxide was seen after the second half of the ALD cycles; neither the Ru oxidation state alternation nor the elimination of some Ru from the surface were observed when using H·. The deposited Ru was determined, by combining results from angle-resolved XPS (ARXPS) and low-energy ion scattering (LEIS) experiments, to grow as 3D nanoparticles rather than as a layer-by-layer 2D film, presumably because the Ru precursor preferentially adsorbs (and decomposes more cleanly) on the metal surface. A discussion is provided of the implications of these results for the design of ALD processes.

Plasma-enhanced atomic layer deposition of ruthenium metal on free-standing carbon nanotube forest for 3D flexible binder-less supercapacitor electrodes

Plasma-enhanced atomic layer deposition of ruthenium on functionalized free-standing multi-walled carbon nanotube (MWCNT) forest directly grown on a stainless steel mesh as a flexible supercapacitor electrode is done by a zero-oxidation state precursor and nitrogen plasma. Using this method for the fabrication of 3D flexible supercapacitor electrodes eliminates the need for any binder component and solution-based synthesis step as well as the production of any toxic by-products. Moreover, it enables the utilization of the entire high-surface-area MWCNTs and it alleviates the Ru agglomeration issue typically found in solution-based synthesis techniques. Accordingly, ruthenium is successfully deposited on the entire length of the carbon nanotubes in various process temperatures and plasma exposure durations with a thickness range of 15–60 nm. Electrochemical characterization of the electrodes shows a significant improvement in the capacitance of Ru coated MWCNT compared to bare MWCNT due to the additional surface faradaic redox reactions. Cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) are carried out to evaluate the electrochemical performance of the fabricated electrodes. The capability of the 3D flexible electrode is evaluated in different bending angles of 60, 80, and 180° and twisting conditions. Capacitance as high as 1834.5 mF.cm−2 (393 F.g−1) with a very low charge transfer resistance of 5.49 Ω.cm−2 is achieved that shows >400 % improvement in capacitance compared to bare MWCNTs. A capacitance retention of 92 % after 1000 CV cycles is achieved.

Atomic Layer Deposition of Ruthenium Dioxide Thin Films Using RuO4 and Alcohols As Reactants

Ruthenium dioxide (RuO2) is the most stable oxide of Ru and has attracted tremendous attention in different applications such as supercapacitors, catalysis, and electrochemical devices. The high conductivity, good chemical stability, a work function value that is even higher than metallic Ru are few properties that make this material so demanding1. Although RuO2 is such an interesting material, atomic layer deposition (ALD) literature reports on this material are scarce. The existing ALD processes based on metalorganic Ru precursors necessitate careful tuning of the O2 partial pressure in order to deposit RuO2 films, as Ru metal is produced at lower O2 partial pressures. Furthermore, reported processes often require high temperature (>180°C) depositions and suffer from high nucleation delays, up to several hundred cycles in some cases.2 In this scenario, we present a novel ALD strategy solely for the synthesis of RuO2 films that takes advantage of the reaction between various alcohols and ruthenium tetroxide (RuO4) without any significant nucleation delay. The process, which uses methanol and RuO4 as reactants, exhibits a growth per cycle (GPC) of 1 angstrom (Å) per cycle (Figure 1a and 1b) at a substrate temperature as low as 60 °C. A constant GPC of 1Å is obtained in the temperature window of 60 °C-120 °C, while the RuO4 precursor is known to decompose above 125 °C.3 The depositions result in amorphous RuO2 films, as confirmed with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. The films can be transformed into crystalline rutile RuO2 by annealing in helium or air at around 400 °C (Figure 1c). The films are conductive, as is evident from the resistivity value of 230 µΩ.cm for a 20 nm film, and the conductivity improved slightly after the anneal.Interestingly, the reaction of other alcohol molecules such as ethanol, 1-propanol, and 2-propanol with RuO4 results in a higher GPC compared to the methanol-based process and it is concluded that the GPC can be increased by increasing the number of carbon atoms in the alcohol chain (Figure 1d). However, all these processes employing different alcohols display typical self-saturating ALD properties. The reaction mechanism of the developed ALD approach was studied in depth using in situ mass spectrometry and in vacuo XPS studies. A reaction mechanism is proposed based on these learnings, wherein during the first half-cycle, alcohol molecules are oxidized into aldehyde and H2O on a RuO2 surface. This in turn causes the partial reduction of the surface RuO2 layer into RuOx or Ru. During the next half-cycle RuO4 oxidizes the surface back to RuO2 and additional RuO2 is deposited on the surface. References Ryden, W.; Lawson, A.; Sartain, C. C., Electrical Transport Properties of Ir O 2 and Ru O 2. Physical Review B 1970, 1 (4), 1494.Austin, D. Z.; Jenkins, M. A.; Allman, D.; Hose, S.; Price, D.; Dezelah, C. L.; Conley Jr, J. F., Atomic layer deposition of ruthenium and ruthenium oxide using a zero-oxidation state precursor. Chemistry of Materials 2017, 29 (3), 1107-1115.Minjauw, M. M.; Dendooven, J.; Capon, B.; Schaekers, M.; Detavernier, C., Atomic layer deposition of ruthenium at 100° C using the RuO 4-precursor and H 2. Journal of Materials Chemistry C 2015, 3 (1), 132-137. This work is funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No.765378. Figure 1

Area-Selective Atomic Layer Deposition of Ruthenium Using a Novel Ru Precursor and H2O as a Reactant

Area-Selective Atomic Layer Deposition of Ruthenium Using a Novel Ru Precursor and H₂O as a Reactant

Atomic layer deposition of Ruthenium on different interfaces for an advanced metallization system of ICs

Nucleation effects were experimentally studied for ruthenium thin films grown by plasma-enhanced atomic layer deposition (PEALD) using O2 plasma. Bis(ethylcyclopentadienyl)ruthenium (II) (Ru(EtCp)2) was used as Ru precursor. The films with the thickness 10 nm on different underlying thin layers (interfaces), including Si, SiO2, Ta2O5, TiN, and TaN were deposited to investigate the effects of interfaces for nucleation of the Ru in ALD process. Some of the samples were previously processed in ammonia and oxygen plasma to enhance nucleation. The processes of forming barrier layers based on titanium and tantalum nitrides by plasma-enhanced atomic layer deposition were also studied. Films properties were evaluated by spectral ellipsometry, scanning electron microscopy and atomic force microscopy.

Atomic layer deposition of ruthenium using an ABC-type process: Role of oxygen exposure during nucleation

Atomic layer deposition (ALD) of ruthenium is of interest for various applications in nanoelectronics and is currently gaining attention for its potential role in interconnect technology in future technology nodes. This work provides insights into the influence of the O2 pulse time on the film nucleation on SiO2 and on the resulting material properties. Ru thin films were deposited using a three-step ALD process consisting of ethylbenzene(1,3-butadiene)Ru(0) precursor, O2 gas, and H2 gas pulses. It is shown that the addition of an H2 pulse to a conventional two-step process reduces any RuOx formed during the O2 pulse to metallic Ru. This provides the opportunity to employ longer O2 pulses, which enhances nucleation, leading to faster growth initiation and smooth films. Using this process, the deposition of Ru films at 225 °C with a low oxygen impurity level (<4 at. %) and a resistivity of 26 ± 2 μΩ cm is demonstrated. The data illustrate that the dosing time required for saturation during the nucleation phase can substantially deviate from the conditions required for the steady-growth phase.

Defect Mitigation in Area‐Selective Atomic Layer Deposition of Ruthenium on Titanium Nitride/Dielectric Nanopatterns

AbstractArea‐selective deposition (ASD) receives increasing attention as a bottom‐up approach for nanoelectronic device fabrication. Uptake of ASD is however limited by defects, which manifest as undesired particle growth on the nongrowth surface. A defect mitigation solution is demonstrated for Ru ASD on TiN/SiO2 nanopatterns by making use of the size‐dependent Ru nanoparticle reactivity. During the initial stages of 1‐(ethylbenzyl)‐1,4‐(ethylcyclohexadienyl)ruthenium and oxygen (EBECHRu/O2) atomic layer deposition (ALD) on dielectrics, Ru particles are too small to catalytically dissociate oxygen, and their growth is suppressed. This phenomenon creates an ASD process window in which particles can be completely etched while retaining the integrity of the ASD pattern on a TiN growth surface. Decreasing the ALD temperature strongly suppresses defect growth, which can be used to expand the process window for ASD. The ASD process window is confirmed by self‐focusing secondary ion mass spectrometry (SF‐SIMS) with its low limit of detection while analyzing 104 structures simultaneously. No defects are detected for Ru ASD on 36 nm TiN/SiO2 patterns by SF‐SIMS. The Ru ASD process is applied for bottom‐up block patterning and functional hardmask patterns are obtained on 300 mm wafers. The approach followed in this work can produce defect‐free ASD processes for a wide variety of applications.

Correction to Atomic Layer Deposition of Ruthenium and Ruthenium Oxide Using a Zero Oxidation State Precursor

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to Atomic Layer Deposition of Ruthenium and Ruthenium Oxide Using a Zero Oxidation State PrecursorDustin Z. AustinDustin Z. AustinMore by Dustin Z. Austinhttp://orcid.org/0000-0001-9580-4711, Melanie A. JenkinsMelanie A. JenkinsMore by Melanie A. Jenkinshttp://orcid.org/0000-0002-9257-8250, Derryl AllmanDerryl AllmanMore by Derryl Allman, Sallie HoseSallie HoseMore by Sallie Hose, David PriceDavid PriceMore by David Price, Charles L. DezelahCharles L. DezelahMore by Charles L. Dezelah, and John F. Conley Jr.*John F. Conley, Jr.More by John F. Conley, Jr.Cite this: Chem. Mater. 2018, 30, 24, 8983–8984Publication Date (Web):December 7, 2018Publication History Published online7 December 2018Published inissue 26 December 2018https://doi.org/10.1021/acs.chemmater.8b04816Copyright © 2018 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1197Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (872 KB) Get e-Alerts Get e-Alerts

Diffusion‐Mediated Growth and Size‐Dependent Nanoparticle Reactivity during Ruthenium Atomic Layer Deposition on Dielectric Substrates

AbstractUnderstanding the growth mechanisms during the early stages of atomic layer deposition (ALD) is of interest for several applications including thin film deposition, catalysis, and area‐selective deposition. The surface dependence and growth mechanism of (ethylbenzyl)(1‐ethyl‐1,4‐cyclohexadienyl)ruthenium and O2 ALD at 325 °C on HfO2, Al2O3, OH, and SiOSi terminated SiO2, and organosilicate glass (OSG) are investigated. The experimental results show that precursor adsorption is strongly affected by the surface termination of the dielectric, and proceeds most rapidly on OH terminated dielectrics, followed by SiOSi and finally SiCH3 terminated dielectrics. The initial stages of growth are characterized by the formation and growth of Ru nanoparticles, which is mediated by the diffusion of Ru species. Mean‐field and kinetic Monte Carlo modeling show that ALD on OSG is best described when accounting for (1) cyclic generation of new nanoparticles at the surface, (2) surface diffusion of both atomic species and nanoparticles, and (3) size‐dependent nanoparticle reactivity. In particular, the models indicate that precursor adsorption initially occurs only on the dielectric substrate, and occurs on the Ru nanoparticles only when these reach a critical size of about 0.85 nm. This phenomenon is attributed to the catalytic decomposition of oxygen requiring a minimum Ru nanoparticle size.

Doping of Graphene By Atomic Layer Deposition of Ruthenium

Graphene has received enormous attention from both academia and industry owing to its excellent electrical, optical, chemical, and mechanical properties. A combination of properties makes graphene a strong candidate for the next generation of flexible and transparent conductive electrode (TCE) materials, but in practice the sheet resistance of a single, as-grown layer of graphene is still not sufficient for this purpose. One of the methods for creating highly conductive graphene films is to increase the charge carrier density through doping. Here, we propose a novel method of graphene doping based on atomic layer deposition (ALD). Ideally, adsorption of precursor should be suppressed on clean surface of graphene since the surface is inert without dangling bonds and chemically active functional group. Defects (e.g., grain boundaries, wrinkles, cracks, holes and residual material) work as selective nucleation sites. Ru is selected due to it having a well-established precursor and recipe and the difference in work function between graphene and Ru can also allow for work function tuning and carrier generation. The sheet resistance of graphene synthesized by chemical vapor deposition is found to be significantly reduced by the selective atomic layer deposition (ALD) of Ru onto defect sites such as wrinkles and grain boundaries. With 200 ALD cycles, the sheet resistance is reduced from ~500 Ω/sq to <50 Ω/sq and the p-type carrier density is drastically increased from 1013 cm-2 to 1015 cm-2. At the same time, the carrier mobility is reduced from ~670 cm2V-1s-1 to less than 100 cm2V-1s-1. This doping of graphene proved to be very stable, with the electrical properties remaining unchanged over 8 weeks of measurement. The selective deposition of Ru on defect sites also makes it possible to obtain a graphene film that is both highly transparent and electrically conductive (e.g., a sheet resistance of 125 Ω/sq with 92 % optical transmittance at 550 nm). The increase in the work function of graphene from 4.6 to 5.1 eV with Ru ALD provides clear evidence of hole carrier generation as a result of an electronic interaction between graphene and Ru. This demonstration of strong and stable doping of graphene with a high optical transmittance is therefore expected to contribute to the use of graphene as a TCE, and in other fields. Figure 1. Ru ALD on graphene. (a) TEM images of graphene after 20 cycles of Ru ALD. (b) Sheet resistance of graphene as a function of the number of ALD cycles. Inset of (b) shows sheet resistance as a function of time. Reference Minsu Kim et al, ACS Appl. Mater. Interfaces, Article ASAP Figure 1

Highly Stable and Effective Doping of Graphene by Selective Atomic Layer Deposition of Ruthenium.

The sheet resistance of graphene synthesized by chemical vapor deposition is found to be significantly reduced by the selective atomic layer deposition (ALD) of Ru onto defect sites such as wrinkles and grain boundaries. With 200 ALD cycles, the sheet resistance is reduced from ∼500 to <50 Ω/sq, and the p-type carrier density is drastically increased from 1013 to 1015 cm-2. At the same time, the carrier mobility is reduced from ∼670 to less than 100 cm2 V-1 s-1. This doping of graphene proved to be very stable, with the electrical properties remaining unchanged over eight weeks of measurement. Selective deposition of Ru on defect sites also makes it possible to obtain a graphene film that is both highly transparent and electrically conductive (e.g., a sheet resistance of 125 Ω/sq with 92% optical transmittance at 550 nm). Highly doped graphene layers achieved by Ru ALD are therefore expected to provide a viable basis for transparent conducting electrodes.

Atomic Layer Deposition of Ruthenium with TiN Interface for Sub-10 nm Advanced Interconnects beyond Copper.

Atomic layer deposition of ruthenium is studied as a barrierless metallization solution for future sub-10 nm interconnect technology nodes. We demonstrate the void-free filling in sub-10 nm wide single damascene lines using an ALD process in combination with 2.5 Å of ALD TiN interface and postdeposition annealing. At such small dimensions, the ruthenium effective resistance depends less on the scaling than that of Cu/barrier systems. Ruthenium effective resistance potentially crosses the Cu curve at 14 and 10 nm according to the semiempirical interconnect resistance model for advanced technology nodes. These extremely scaled ruthenium lines show excellent electromigration behavior. Time-dependent dielectric breakdown measurements reveal negligible ruthenium ion drift into low-κ dielectrics up to 200 °C, demonstrating that ruthenium can be used as a barrierless metallization in interconnects. These results indicate that ruthenium is highly promising as a replacement to Cu as the metallization solution for future technology nodes.

Atomic layer deposition of ruthenium on plasma-treated vertically aligned carbon nanotubes for high-performance ultracapacitors

It is challenging to realize a conformal metal coating by atomic layer deposition (ALD) because of the high surface energy of metals. In this study, ALD of ruthenium (Ru) on vertically aligned carbon nanotubes (CNTs) was carried out. To activate the surface of CNTs that lack surface functional groups essential for ALD, oxygen plasma was applied ex situ before ALD. X-ray photoelectron spectroscopy and Raman spectroscopy confirmed surface activation of CNTs by the plasma pretreatment. Transmission electron microscopy analysis with energy-dispersive x-ray spectroscopy composition mapping showed that ALD Ru grew conformally along CNTs walls. ALD Ru/CNTs were electrochemically oxidized to ruthenium oxide (RuOx) that can be a potentially useful candidate for use in the electrodes of ultracapacitors. Electrode performance of RuOx/CNTs was evaluated using cyclic voltammetry and galvanostatic charge–discharge measurements.

Atomic Layer Deposition of Ruthenium on a Titanium Nitride Surface: A Density Functional Theory Study

Because of its excellent properties in nanotechnology applications, atomic layer deposition of ruthenium (Ru) has been the subject of numerous experimental studies. Recently, two different Ru precursors were compared for plasma-enhanced atomic layer deposition (PEALD) of Ru, and their reactivity was found to be different. Inhibition was observed for bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)2), while nearly linear growth behavior was observed for (methylcyclopentadienyl-pyrrolyl)ruthenium (Ru(MeCp)Py). To understand this difference in reactivity, we investigate the adsorption of RuCp2 and RuCpPy (i.e., without substituents) on a TiN surface using calculations based on periodic boundary conditions density functional theory (DFT) combined with experiments based on Rutherford backscattering spectroscopy (RBS). The calculations demonstrate that the RuCpPy precursor chemisorbs on the TiN(100) surface while the RuCp2 precursor only physisorbs. We propose a reaction mechanism for the chemisorption of RuCpPy. The area density of the calculated RuCpPy surface species is compared with the experimental values from RBS. The impact of a H-plasma is also investigated. The DFT calculations and experimental results from RBS provide insight into the adsorption processes of the RuCpPy and RuCp2 precursors on the TiN(100) surface.

Atomic Layer Deposition of Ruthenium in Various Precursors and Oxygen Doses

Atomic layer deposition (ALD) of Ru films under various precursor and oxidant supply conditions was carried out at 320{degree sign}C on silicon wafers. The Ru precursor used was bis(ethylcyclopentadienyl) ruthenium [Ru(EtCp)2], and oxygen gas was used as the oxidant. The Ru precursor pulse time, oxygen pulse time, and oxygen flow rate were varied, and the effects of these parameters on the morphology of the deposited films were analyzed using scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. The films showed hollow shell-like bumps, indicating that film growth began with a reaction in the gas phase or in physically adsorbed states. A mismatch between the thermal expansion coefficients of Si and Ru or the existence of residues on the wafer surfaces was suspected to be responsible for the hollow shell-like structures. However, the results of energy-dispersive X-ray spectroscopy (EDS) proved that the latter was not the case.

Atomic Layer Deposition of Ruthenium in Various Precursor and Oxygen Doses

not Available.

Microcontact Printed RuOx Film as an Activation Layer for Selective-Area Atomic Layer Deposition of Ruthenium

Selective-area atomic layer deposition (ALD) was achieved using microcontact printed RuOx films as an activation layer for ruthenium ALD process. Patterned RuOx films were prepared by transferring RuCl3 layer by a PDMS (polydimethylsiloxane) stamp to Si(100) substrate and exposing this layer to ozone. Patterned films had either 1.5 μm or about 500 nm wide RuOx lines. Ruthenium was deposited on the activated areas at 250 °C. At this temperature the ruthenium did grow only on the activated areas but not on silicon so that the features of the stamps were repeated on the substrate.

The low temperature atomic layer deposition of ruthenium and the effect of oxygen exposure

We have studied the atomic layer deposition (ALD) of ruthenium using bis(2,4-dimethylpentadienyl) ruthenium and oxygen. We show that the process is achievable at a low operating temperature of 185 °C. Variation in the exposure time and pressure of the oxygen counterreactant has significant effects on the nucleation, growth rate and composition of the deposited ruthenium films. High oxygen pressure helps to promote the nucleation of ruthenium on a silicon dioxide substrate. Although saturation conditions are achieved with the Ru precursor, saturation of the ruthenium growth rate with oxygen exposure is observed only for a small range of oxygen exposure. Increasing the oxygen exposure further results in the incorporation of oxygen in the deposited film to form ruthenium oxide, a process which is enhanced at higher deposition temperature. We propose that the slow diffusion of oxygen to the subsurface region is a rate-limiting step in this process. We demonstrate that the composition of the deposited films from metallic ruthenium to ruthenium oxide, as well as the average grain size, may be regulated by tuning the pressure and exposure time of the oxygen counterreactant. Hence, this low temperature ALD process provides a flexible route to the deposition of Ru-based films.