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Magneto-ionics, which deals with the change of magnetic properties through voltage-driven ion migration, is expected to be one of the emerging technologies to develop energy-efficient spintronics. While a precise modulation of magnetism is achieved when voltage is applied, much more uncontrolled is the spontaneous evolution of magneto-ionic systems upon removing the electric stimuli (i.e., post-stimulated behavior). Here, we demonstrate a voltage-controllable N ion accumulation effect at the outer surface of CoN films adjacent to a liquid electrolyte, which allows for the control of magneto-ionic properties both during and after voltage pulse actuation (i.e., stimulated and post-stimulated behavior, respectively). This effect, which takes place when the CoN film thickness is below 50 nm and the voltage pulse frequency is at least 100 Hz, is based on the trade-off between generation (voltage ON) and partial depletion (voltage OFF) of ferromagnetism in CoN by magneto-ionics. This novel effect may open opportunities for new neuromorphic computing functions, such as post-stimulated neural learning under deep sleep., Financial support by the European Research Council (MAGIC-SWITCH 2019-Proof of Concept Grant, Agreement No. 875018), the European Union's Horizon 2020 research and innovation programme (European Training Network, BeMAGIC ETN/ITN Marie Skłodowska-Curie grant No. 861145; and Integrated Infrastructure, RADIATE, grant No. 824096), the Spanish Government (MAT2017-86357-C3-1-R, PID2020-116844RB-C21 and PDC2021-121276-C3), the Generalitat de Catalunya (2017-SGR-292 and 2018-LLAV-00032), the European Regional Development Fund (MAT2017-86357-C3-1-R and 2018-LLAV-00032) and the KU Leuven (BOF program) is acknowledged. A. Q. acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities through the “Severo Ochoa” Programme for Centers of Excellence in R&D (FUNFUTURE CEX2019-000917-S) and the Juan de la Cierva formación contract (FJC2019-039780-I). J. S. thanks the Spanish Fábrica Nacional de Moneda y Timbre (FNMT) for fruitful discussions. The XAS measurements were performed at BL29-BOREAS beamline at ALBA Synchrotron with the collaboration of ALBA staff. We acknowledge service from MiNa Laboratory at IMN, and funding from CM (project S2018/NMT-4291 TEC2SPACE), MINECO (project CSIC13-4E-1794) and EU (FEDER, FSE). E. M. is a Serra Húnter Fellow., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

We investigate differential evolution optimization to fit Rutherford backscattering data. The algorithm helps to find, with very high precision, the sample composition profile that best fits the experimental spectra. The capabilities of the algorithm are first demonstrated with the analysis of synthetic Rutherford backscattering spectra. The use of synthetic spectra highlights the achievable precision, through which it becomes possible to differentiate between the counting statistical uncertainty of the spectra and the fitting error. Finally, the capability of the algorithm to analyze large sets of experimental spectra is demonstrated with the analysis of the position-dependent composition of a Sr[Formula: see text]Ti[Formula: see text]O[Formula: see text] layer on a 200 mm silicon wafer. It is shown that the counting statistical uncertainty as well as the fitting error can be determined, and the reported total analysis uncertainty must cover both.

ispartof: ACS APPLIED ELECTRONIC MATERIALS vol:4 issue:4 pages:1823-1831 status: published

A plasma-enhanced ALD process has been developed to deposit nickel phosphate. The process combines trimethylphosphate (TMP) plasma with oxygen plasma and nickelocene at a substrate temperature of 300 degrees C. Saturation at a growth per cycle of approximately 0.2 nm per cycle is observed for both the TMP plasma and nickelocene, while a continuous decrease in the growth per cycle is found for the oxygen plasma. From ERD, a stoichiometry of Ni-3(P0.8O3.1)(2) is measured, but by adding additional oxygen plasma after nickelocene, the composition of Ni-3(P0.9O3.7)(2) becomes even closer to stoichiometric Ni-3(PO4)(2). The as-deposited layer resulting from the process without the additional oxygen plasma is amorphous but can be crystallized into Ni2P or crystalline Ni-3(PO4)(2) by annealing under a hydrogen or helium atmosphere, respectively. The layer deposited with the additional oxygen plasma shows two X-ray diffraction peaks indicating the formation of crystalline Ni-3(PO4)(2) already during the deposition. The resulting PE-ALD deposited nickel phosphate layers were then electrochemically studied and compared to PE-ALD cobalt and iron phosphate. All phosphates need electrochemical activation at low potential first, after which reversible redox reactions are observed at a potential of approximately 2.5 V vs. Li+/Li. A relatively high capacity and good rate behavior are observed for both nickel and cobalt phosphate, which are thought to originate from either a conversion type reaction or an alloying reaction.

ispartof: ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS vol:8 issue:9 pages:818-824 status: published

Il continuo down-scaling dei transistor ha permesso il raggiungimento di una eccezionale miniaturizzazione. Cio ha reso la resistenza di contatto parte preponderante della resistenza parassita del dispositivo. In questa tesi si riporta la caratterizzazione layer epitassiali drogati con Fosforo, Arsenico e Co-drogati (Si:P, Si:As, Si:P:As) per NMOS S/D. La Deposizione Chimica da Vapore e stata impiegata per un processo selettivo a 670 °C e uno non-selettivo a una temperature piu bassa di 450 °C. Sono state studiate le proprieta fisiche come morfologia, qualita cristallina, composizione, attivazione dei dopanti ed e stata verificata la stabilita termica sino a 700 °C. Variando la concentrazione dall' 1% al 4% sono stati esplorati scenari differenti. La resistivita del contatto e stata misurata su stacks, realizzate impiegando la Ti-silicidation, per mezzo della tecnica MR-CTLM. I risultati mostrano che per i layer, realizzati alla temperatura di 670 °C a concentrazioni totali elevate (~3%), la concentrazione attiva del Si:As e Si:P:As layer e generalmente piu bassa se comparata al Si:P, inoltre il Si:As mostra minore tensile strain. I layer co-drogati realizzati con il processo non-selettivo e a basse concentrazioni totali (~1.2%) sono caratterizzati da una maggiore concentrazione attiva dovuta a un meccanismo di vacancy trapping piu efficiente, mentre non si osservano miglioramenti tangibili dopo aver applicato laser annealing. La resistivita del contatto misurata su Ti-stack raggiunge 2 · 10−9 Ω .cm2 per differenti condizioni di processo. L'introduzione di As mostra effetti positivi nella resistenza di contatto dei layer as-grown ~3% per il processo selettivo. I layer epitassiali realizzati in Si:As e Si:P:As realizzati a 450 °C mostrano ρc comparabile a quelli drogati con Fosforo (Si:P). Queste proprieta insieme a una riduzione della diffusione per effetto di rapid-thermal-annealing rendono Si:As and Si:P:As materiali promettenti per NMOS S/D.

The present study reports the impact of process conditions and post annealing treatment on the stress and physico-chemical properties in different types of plasma enhanced atomic layer deposited (PEALD) SiNx films. More specifically, the SiNx films deposited at 500 °C were annealed subsequently at 1000 °C in N2 ambient for different times ranging between 30 and 6750 s and were subjected to thickness, mass, refractive index, chemical bonds and structure, H content, N/Si stoichiometry, morphology, roughness, and uniformity monitoring. Depending on the deposition process conditions, we confirm the possibility to form, at 500 °C with PEALD, some very compressive SiN films with reduced hydrogen content by controlling the plasma conditions along the deposition process. More interestingly, these compressive films with low hydrogen concentration exhibit high thermo-mechanical stability compared to hydrogenated PEALD and plasma enhanced chemical vapor deposition silicon nitride from this study or reported in the literature, films which typically tend to become tensile with a similar annealing sequence. These results confirm the importance of the plasma power to engineer the as-deposited silicon nitride stress but also highlight the role of hydrogen in the thermal instability of these layers, a low H concentration being needed for a better mechanical stability.

Background: An extreme ultraviolet (EUV)-transparent pellicle must be used during lithography to protect the photomask from fall-on particles. A pellicle made of free-standing carbon nanotube (CNT) films stops particles despite the presence of gaps while demonstrating high EUV transmission, mechanical stability, low EUV scattering and reflectivity, and DUV transmission that enables through-pellicle mask inspection. Aim: The CNT EUV pellicle properties can be tailored based on the diversity of CNT structures and tunability of their configuration within the CNT film (density, bundle size, composition, etc.) as shown in this work. A remaining challenge is extending the CNT EUV pellicle lifetime in the scanner environment of EUV-induced hydrogen-based plasma, and the effects on different CNT films are explored here. Approach: Optical and thermal properties of different CNT pellicles with respect to the CNT material type, density, composition, and bundle size were explored. The ability of uncoated CNT EUV pellicles to withstand high EUV powers in the hydrogen-based environment was tested. Transmission, spectroscopic, and chemical mapping of the exposed CNT membranes were performed to explore the material modifications under various exposure conditions. Results: Uncoated CNT pellicles withstand 600-W source power equivalent in the EUV scanner-like gas environment but exhibit structural changes with prolonged exposure. Multiwalled CNT pellicles exhibit less EUV transmission change as compared to single-walled CNT pellicles under the same exposure conditions. The protection of CNT material from structural degradation by means of coating was shown. Conclusions: These investigations add to the understanding of CNT EUV pellicle tunability for optimal performance and lifetime limiters of CNT pellicles under the influence of EUV radiation and plasma. We anticipate the need for coating the CNT pellicle to protect the CNT material against plasma damage for the current scanner conditions. Optimization of both the CNT membrane and its coating is in progress.

In this study, we explored the key properties and functionalities of plasma enhanced atomic layer deposition (PEALD) SiNx films, synthesized using different deposition temperatures (500–550 °C) and plasma conditions (lower and higher), both on 300 mm blanket Si and on several integrated 3D topology substrates, at the thicknesses relevant for diverse nanoscale applications. Our study shows that with an increase of temperature (500–550 °C), a small reduction in HF wet etch rate (1.1–0.69 nm/min), and H content (9.6% vs 7.4%) was observed. When using higher plasmas, significant improvements in blanket properties were observed. The films were denser (2.95 g/cm3), exhibited lower H content (2.4%), showed better etch rates (0.39 and 0.44 nm/s for HF and CF4 based), and SiNx grew without any nucleation delay on alternative Si1−xGex channel surfaces. The vertical and lateral conformality was found to be similar and appears not to be impacted with the plasma conditions. Extensive steam oxidation barrier studies performed at the sidewalls of different aspect ratio lines showed the PEALD SiNx liner scaling potentiality down to 1 nm when deposited using higher plasma. In addition, the outer gate and inner spacer properties were found to be superior (with lower loses) for higher plasma films when subjected to several dry etch, strips, and H3PO4 chemistries. The outstanding conformality (90%–95% on aspect ratios ≤10:1) combined with excellent high end material properties in the ultrathin regimes (1–10 nm) corroborate the virtue of PEALD SiNx toward integration in scaled down and advanced nanoelectronics device manufacturing.

As critical dimensions in integrated circuits continue to shrink, the lithography-based alignment of adjacent patterned layers becomes more challenging. Area-selective atomic layer deposition (ALD) allows circumventing the alignment issue by exploiting the chemical contrast of the exposed surfaces. In this work, we investigate the selective deposition of TiO2 by plasma halogenation of amorphous carbon (a-C:H) acting as a growth-inhibiting layer. On a-C:H, a CF4 or Cl2 plasma forms a thin halogenated layer that suppresses the growth of TiO2, while nucleation remains unaffected on plasma-treated SiO2. The same halogenating plasmas preferentially etch TiO2 nuclei over films and thus enable the restoration of the halogenated surface of amorphous carbon. By embedding the intermediate plasma treatments in the ALD TiO2 sequence, an 8 nm TiO2 layer could be deposited with a selectivity of 0.998. The application of the cyclic process on a 60 nm half-pitch line pattern resulted in the defect-free deposition of TiO2 at the bottom of the trenches. Cyclic fluorination demonstrated better growth inhibition compared to chlorination due to more efficient defect removal and retention of the favorable surface composition during plasma exposure. While exploring the TiO2 nucleation defects at the limit of detection for conventional elemental analysis techniques (

Nanosheet Field-Effect Transistors (FETs) are candidates to replace today’s finFETs as they offer both an enhanced electrostatic control and a reduced footprint. The processing of these devices involves the selective lateral etching, also called cavity etch, of the SiGe layers of a vertical Si/SiGe superlattice, to isolate the future vertically stacked Si channels. In this work, we evaluate the capabilities of various conventional Critical Dimension (CD) and alternative spectroscopic techniques for this challenging measurement of a buried CD. We conclude that Raman and energy-dispersive X-ray spectroscopies are very promising techniques for fast inline cavity depth measurements.

Research on carbon nanotube (CNT) films for the EUV pellicle application was initiated at imec in 2015 triggered by the remarkable optical, mechanical, and thermal properties of the CNT material. Today the advancement of the CNT material synthesis together with matured methods to fabricate thin CNT membranes make free-standing CNT films a very promising EUV pellicle candidate for high volume EUV lithography. Balancing the CNT material properties for the optimal pellicle performance in EUV scanners remains the ongoing research focus. Depending on the density and morphology of the CNTs within the film and individual CNT parameters, like number of walls, bundle size, metal catalyst content, purity etc., the optical and thermal properties of the CNT pellicle can be tuned. It is critical for the pellicle to be stable in the EUV lithography scanner environment which includes hydrogen plasma and heat loads associated with high powers beyond 250 W. Different types of CNTs, i.e. single-, double-, multi-walled CNTs and their combinations, are explored as building blocks of an optimized pellicle membrane. Optical properties of different pellicles and their ability to withstand high EUV powers in the hydrogen-based environment were tested. Transmission, spectroscopic and chemical composition mapping of the exposed free-standing CNT films are used to study the material changes that occur in the scanner-like environment. A solution is needed to extend the CNT pellicle lifetime and coating is discussed as a potential approach to protect the CNT material from hydrogen plasma damage.

ispartof: ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY vol:8 issue:6 pages:P346-P350 ispartof: location:MEXICO, Cancun status: published

In this study of nanoscale etching for state-of-the-art device technology the importance of the nature of the surface oxide, is demonstrated for two III-V materials. Etching kinetics for GaAs and InP in acidic solutions of hydrogen peroxide are strikingly different. GaAs etches much faster, while the dependence of the etch rate on the H+ concentration differs markedly for the two semiconductors. Surface analysis techniques provided information on the surface composition after etching: strongly non-stoichiometric porous (hydr)oxides on GaAs and a thin stoichiometric oxide that forms a blocking layer on InP. Reaction schemes are provided that allow one to understand the results, in particular the important difference in etch rate and the contrasting role of chloride in the dissolution of the two semiconductors.

Several applications of two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) in nanoelectronic devices require the deposition of ultrathin pinhole free high-κ dielectric films on 2D TMDs. However, deposition of nm-thin high-κ dielectric films on 2D TMDs remains challenging due to the inert TMD surface. Here, we demonstrate that the surface of a synthetic polycrystalline 2D MoS2 film is functionalized with SiO2 to enable the atomic layer deposition (ALD) of thin and continuous Al2O3 and HfO2 layers. The origins of nucleation, the growth mode, and layer coalescence process have been investigated by complementary physical characterization techniques, which can determine the chemical bonds, absolute amount, and surface coverage of the deposited material. SiO2 is prepared by oxidizing physical vapor deposited Si in air. The surface hydrophilicity of MoS2 significantly increases after SiO2 functionalization owing to the presence of surface hydroxyl groups. SiO2 layers with a Si content of...

The process characteristics, the surface chemistry, and the resulting film properties of Ru deposited by atomic layer deposition from (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl)Ru(0) (EBECHRu) and O2 are discussed. The surface chemistry was characterized by both combustion reactions as well as EBECHRu surface reactions by ligand release. The process behavior on TiN starting surfaces at 325 °C was strongly influenced by Ti(O,N)x segregation on the growing Ru surface with consequences for both the growth per cycle as well as the film properties. For optimized process conditions, the films showed high purity with low C and O concentrations of the order of 1020 at./cm3. Higher deposition temperature led to strong (001) fiber texture of the films on SiO2 starting surfaces. Annealing in forming gas improved the crystallinity and led to resistivity values as low as 11 μΩcm for Ru films with a thickness of 10 nm.

In situ nitrogen doping of aluminum phosphate has been investigated in two different plasma-enhanced atomic layer deposition (PEALD) processes. The first method consisted of the combination of trimethyl phosphate plasma (TMP*) with a nitrogen plasma and trimethyl aluminum (TMA), that is, TMP*-N-2*-TMA. The second method replaces TMP* with a diethylphosphoramidate plasma (i.e., DEPA*-N-2*-TMA) of which the amine group could further aid nitrogen doping and/or eliminate the need for a nitrogen plasma step. At a substrate temperature of 320 degrees C, the TMP*-based process showed saturated growth (0.8 nm/cycle) of a nitrogen-doped (approximately 8 atom %) Al phosphate, while the process using DEPA* showed a similar amount of nitrogen but a significantly higher growth rate (1.4 nm/cycle). In the latter case, nitrogen doping could also be achieved without the nitrogen plasma, but this leads to a high level of carbon contamination. Both films were amorphous as-deposited, while X-ray diffraction peaks related to AlPO4 appeared after annealing in a He atmosphere. For high coating thickness (>2 nm), a significant increase in the Li-ion transmittance was found after nitrogen doping, although the coating has to be electrochemically activated. At lower thickness scales, such activation was not needed and nitrogen doping was found to double the effective transversal electronic conductivity. For the effective transversal ionic conductivity, no conclusive difference was found. When a lithium nickel manganese cobalt oxide (NMC) powder is coated with one ALD cycle of N-doped Al phosphate, the rate capability and the energy efficiency of the electrode improves.

The increasing scientific and industry interest in 2D MX

Robust and scalable thin film deposition methods are key to realize the potential of metal-organic frameworks (MOFs) in electronic devices. Here, we report the first integration of the chemical vapor deposition (CVD) of MOF coatings in a custom reactor within a cleanroom setting. As a test case, the MOF-CVD conditions for ZIF-8 are optimized to enable smooth, pinhole-free, and uniform thin films on full 200 mm wafers under mild conditions. The single-chamber MOF-CVD process and the impact of the deposition parameters are elucidated via a combination of in situ monitoring and ex situ characterization. The resulting process guidelines will pave the way for new MOF-CVD formulations and a plethora of MOF-based devices.

In this work, the authors demonstrate that Rutherford backscattering spectrometry (RBS) can be extended from a metrology concept applied to blanket films toward a method to analyze confined nanostructures. By a combination of measurements on an ensemble of devices and extensive simulations, it is feasible to quantify the composition of InGaAs nanostructures (16–50 nm) embedded periodically in an SiO2 matrix. The methodology is based on measuring multiple fins simultaneously while using the geometrical shape of the structures, obtained from a transmission electron microscopy analysis, as input for a multitude of trajectory calculations. In this way, the authors are able to reproduce the RBS spectra and to demonstrate the sensitivity of the RBS spectra to the quantitative elemental composition of the nanostructures and to variations of their shape and mean areal coverage down to one nanometer. Thus, the authors establish RBS as a viable quantitative characterization technique to probe the composition and structure of periodic arrays of nanostructures.In this work, the authors demonstrate that Rutherford backscattering spectrometry (RBS) can be extended from a metrology concept applied to blanket films toward a method to analyze confined nanostructures. By a combination of measurements on an ensemble of devices and extensive simulations, it is feasible to quantify the composition of InGaAs nanostructures (16–50 nm) embedded periodically in an SiO2 matrix. The methodology is based on measuring multiple fins simultaneously while using the geometrical shape of the structures, obtained from a transmission electron microscopy analysis, as input for a multitude of trajectory calculations. In this way, the authors are able to reproduce the RBS spectra and to demonstrate the sensitivity of the RBS spectra to the quantitative elemental composition of the nanostructures and to variations of their shape and mean areal coverage down to one nanometer. Thus, the authors establish RBS as a viable quantitative characterization technique to probe the composition and st...

© 2018 Elsevier B.V. Quantum Dots (QDs) are considered as an efficient building block of many optoelectronic applications, such as semiconductor laser, photodetector, whereby their physical dimension is the key parameter to be controlled. In this work, we have studied experimentally the growth of InAs QDs on InP(0 0 1) substrate by MOVPE and established a theoretical model explaining the observed epitaxial behaviour. In variance with the classical Stranski-Krastanov growth, we show that during the growth there is an intermediate stage whereby although first large 3D islands are formed, an increased density of small QDs is formed concurrent with the shrinkage of the large 3D islands. As a result, the growth can be divided into three regimes: 2D layer growth, large 3D islands growth and QDs growth. To explain this evolution, a thermodynamic model has been developed accounting for the process driven by surface energy, elastic relaxation energy and inter-island interaction energy. It will be shown that the balance between the surface energy and the elastic relaxation energy provides the transition from 2D layer to large 3D islands (around at 3 ML of InAs growth). This model also supports the energetically favourable truncated pyramidal shape for large 3D islands and the spherical cap shape for QDs. We show in this paper that a balance between surface energy, elastic relaxation energy and inter-island elastic interaction explains the volume shrinkage of the early large 3D islands towards the formation of small QDs in high density. ispartof: JOURNAL OF CRYSTAL GROWTH vol:509 pages:133-140 status: published

The use of Ti phosphate as a functional coating for Li ion battery electrodes has been investigated, as well as the effect of nitrogen doping on its electrochemical properties. First, previous knowledge on PE-ALD of Ti phosphate (using an exposure sequence of trimethylphosphate plasma–oxygen plasma–titaniumisopropoxide) was used to study an altered process using a nitrogen plasma, i.e. TMP* - N2* - TTIP. This enabled the deposition of a nitrogen doped (6 at.%) Ti phosphate with a growth per cycle of 0.4 nm/cycle. Next, a dual-source precursor (diethylphosphoramidate plasma, or DEPA*) was introduced instead of TMP*, allowing for a higher growth rate (0.6 nm/cycle) and a higher nitrogen level (8.6 at.%). The ionic transparency of the phosphate slightly decreased due to nitrogen incorporation, but the effective transversal electronic conductivity showed to be three times higher after nitrogen doping. A 2 nm coating of (un)doped Ti phosphate significantly improved the rate capability of a lithium nickel manganese cobalt oxide (NMC) electrode, increasing the amount of energy that can be stored at high (dis)charging speeds with a factor 10 (at 5C). In addition, the undoped titanium phosphate coating offered increased stability, retaining 84% of the capacity after 100 cycles at 1C with respect to 79% for the uncoated electrode.

Hafnium zirconate (HZO) is investigated in metal–ferroelectric–metal capacitors as a function of Hf/(Hf+Zr) atomic ratio, the presence of a thin ZrO 2 seed layer, and/or by doping HZO with La 3+. It is demonstrated that a longer endurance is achieved with Hf-rich HZO by introducing a ZrO 2 seed layer. The endurance is further improved by introducing La 3+ in the Hf-rich HZO layer of the bilayer stack, which offers a higher 2P r in the pristine state compared with a stoichiometric HZO doped with the same amount of La 3+. Both ZrO 2 underlayer and La 3+ doping of HZO are shown to play a decisive role in promoting the formation of an orthorhombic and tetragonal phase at the expense of a detrimental monoclinic phase.

For porous low-k film to be integrated into the next generation of interconnects, the pores need to be sealed against metal ions and barrier precursors. Self-assembled monolayers (SAMs) from organosilane precursor are spin coated onto 300mmk=2.2 low-k wafers. Two solvents, propylene glycol monomethyl ether acetate (PGMEA) and methanol with different dielectric constant of 8.3 and 20.1, are evaluated in terms of SAMs layer quality and sealing efficiency at coupon level. SAMs deposited from PGMEA show better sealing than SAMs deposited from methanol and therefore are selected for upscaling. Full wafer spin coating results show that a concentration of 0.05mM or below results in a partial coverage and a tilt angle as high as 70° from the backbone to the normal. Aggregation is observed for all tested concentrations and is worse for higher concentrations, which is possibly induced by the non-negligible presence of water in PGMEA solvents. In order to test the sealing efficiency of the SAMs layer against metal barrier precursors, MnN films by chemical vapor deposition (CVD) and TaNx/Ta (TNT) films by physical vapor deposition (PVD) are deposited on SAM coated low-k wafers. HfO2 is also deposited by Atomic layer deposition (ALD), which is not considered as a barrier but to test the sealing against ALD precursors. Depth profiling Rutherford Backscattering Spectrometry (RBS) measurements indicate an effective sealing of SAMs against CVD and ALD precursors but not against PVD barrier. Display Omitted SAMs are spin coated onto 300mm low-k wafers. After SAMs deposition, źk is 0.1 and decreases to 0.03 after annealing.Solvent dielectric constant affect the pre-condensation of SAMs and therefore sealing.RBS measurements shows that SAMs seal against MnN by CVD but not TNT by PVD.

The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si epitaxy on O atomic layers (ALs) with different O-contents and structures. O ALs are deposited by ozone (O3) or oxygen (O2) exposure on H-terminated Si at 50 °C and 300 °C respectively. Epitaxial Si is deposited by chemical vapor deposition using silane (SiH4) at 500 °C. After O3 exposure, the O atoms are uniformly distributed in Si-Si dimer/back bonds. This O layer still allows epitaxial seeding of Si. The epitaxial quality is enhanced by lowering the surface distortions due to O atoms and by decreasing the arrival rate of SiH4 reactants, allowing more time for surface diffusion. After O2 exposure, the O atoms are present in the form of SiOx clusters. Regions of hydrogen-terminated Si remain present between the SiOx clusters. The epitaxial seeding of Si in these structures is realized on H-Si regions, and an epitaxial layer grows by a lateral overgrowth mechanism. A breakdown in the epitaxial ordering occurs at a critical Si thickness, presumably by accumulation of surface roughness.

Chemistry of materials XX(XX), acs.chemmater.9b03435 (2019). doi:10.1021/acs.chemmater.9b03435, Robust and scalable thin film deposition methods are key to realize the potential of metal-organic frameworks (MOFs) in electronic devices. Here, we report the first integration of the chemical vapor deposition (CVD) of MOF coatings in a custom reactor within a cleanroom setting. As a test case, the MOF-CVD conditions for ZIF-8 are optimized to enable smooth, pinhole-free, and uniform thin films on full 200 mm wafers under mild conditions. The single-chamber MOF-CVD process and the impact of the deposition parameters are elucidated via a combination of in situ monitoring and ex situ characterization. The resulting process guidelines will pave the way for new MOF-CVD formulations and a plethora of MOF-based devices., Published by American Chemical Society, Washington, DC

© 2018 American Chemical Society. When two-dimensional (2D) group-VI transition metal dichalcogenides such as tungsten disulfide (WS 2 ) are grown by atomic layer deposition (ALD) for atomic growth control at low deposition temperatures (≤450 °C), they often suffer from a nanocrystalline grain structure limiting the carrier mobility. The crystallinity and monolayer thickness control during ALD of 2D materials is determined by the nucleation mechanism, which is currently not well understood. Here, we propose a qualitative model for the WS 2 nucleation behavior on dielectric surfaces during plasma-enhanced (PE-) ALD using tungsten hexafluoride (WF 6 ), dihydrogen (H 2 ) plasma and dihydrogen sulfide (H 2 S) based on analyses of the morphology of the WS 2 crystals. The WS 2 crystal grain size increases from ∼20 to 200 nm by lowering the nucleation density. This is achieved by lowering the precursor adsorption rate on the starting surface using an inherently less reactive starting surface, by decreasing the H 2 plasma reactivity, and by enhancing the mobility of the adsorbed species at higher deposition temperature. Since silicon dioxide (SiO 2 ) is less reactive than aluminum oxide (Al 2 O 3 ), and diffusion and crystal ripening is enhanced at higher deposition temperature, WS 2 nucleates in an anisotropic island-like growth mode with preferential lateral growth from the WS 2 crystal edges. This work emphasizes that increasing the crystal grain size while controlling the basal plane orientation is possible during ALD at low deposition temperatures, based on insight in the nucleation behavior, which is key to advance the field of ALD of 2D materials. Moreover, this work demonstrates the conformal deposition on three-dimensional (3D) structures, with WS 2 retaining the basal plane orientation along topographic structures. ispartof: CHEMISTRY OF MATERIALS vol:30 issue:21 pages:7648-7663 status: published

This article discusses the materials aspects involved in the successful integration of hybrid floating gate (HFG) devices for NAND applications. In HFG, a Si(n type)\metal(p type) stack replaces the standard poly-Si FG. The high work function metal helps to enlarge the program window by limiting the leakage through the high-k intergate dielectric (IGD); the use of high-k IGD enables to scale the equivalent oxide thickness (EOT) of the HFG cell. Our recent progresses in the understanding of the materials characteristics (IGD crystallinity and HFG-IGD thermal stability) that influence memory performance have allowed to demonstrate that HFG can be a solution to scale planar flash beyond the 20 nm node with the best preferable hybrid floating gate structure being a Ru-based HFG and a 3-layers IGD stack of HfAlO\Al2O3\HfAlO. Indeed, through the correct selection and combination of materials for process conditions that are relevant in flash memory fabrication flows, we will show that program windows can be suitably engineered. Finally, the materials challenges for keeping acceptable memory retention characteristics are also highlighted.

In this work we demonstrate a thermally stable copper supply layer by Si alloying of Cu0.6Te0.4 for application in Conductive Bridge Random Access Memory (CBRAM) cells. A good thermal stability of the copper supply layer is necessary to allow its implementation in future memory devices. In situ X-ray diffraction is used to investigate the crystallization behaviour of Cu0.6Te0.4 layers with Si contents up to 20 at%. Low Si concentrations result in crystallization, phase separation and transformations at temperatures below 400 °C, whereas addition of 20 at% Si results in a layer that remains amorphous up to temperatures exceeding 500 °C, making it compatible with back end of line temperatures. Moreover, atomic force microscopy measurements show a very smooth surface morphology up to temperatures exceeding 400 °C. The absence of grain boundaries in the amorphous layer is expected to contribute to the uniformity of the supply layer, and hence it should be beneficial for integration in scaled devices. We attribute the good ability of Si to keep the material amorphous to the high coordination number of Si and the formation of strong bonds which are difficult to break, making rearrangement in a lattice more difficult to proceed. This is further evidenced by XPS measurements, which suggest the occurrence of both Si–Si and Si–Te bonds. CBRAM functionality of this composition is demonstrated by integrating the material in 580 μm diameter dot Pt/Cu–Te–Si/Al2O3/n+ Si CBRAM cells.

The presence of O during the chemical vapour deposition (CVD) of B-doped diamond results in the suppression of B incorporation into the diamond film. In this study, we demonstrate that the amount o ...

In order to integrate k=2.0 p-OSG dielectric materials into the next generation of interconnects, the porous material has to be sealed against metal barrier precursor. For this purpose, the combination of pore stuffing and SAMs was engineered on patterned structures to achieve sealing with minimal plasma damage. First a pore stuffing (P4) approach was implemented to mitigate the plasma damage and to confine the reaction sites to the top surface. Then self-assembled monolayers (SAMs) were deposited from 11-cyanoundecyltrichlorosilane (CNSAM) or (3-aminopropyl)-trimethoxysilane (APTMS) precursor, followed by TiN metal barrier deposition via plasma enhanced-atomic layer deposition (PE-ALD). Pore sealing efficiencies and k value of these samples were benchmarked against standard back end of line (BEOL) CF4 plasma.

The deposition of ultra-thin tungsten films and their related 2D chalcogen compounds on large area dielectric substrates by gas phase reactions is challenging. The lack of nucleation sites complicates the adsorption of W-related precursors and subsequent sulfurization usually requires high temperatures. We propose here a technique in which a thin solid amorphous silicon film is used as reductant for the gas phase precursor WF6 leading to the conversion to metallic W. The selectivity of the W conversion towards the underlying dielectric surfaces is demonstrated. The role of the Si surface preparation, the conversion temperature, and Si thickness on the formation process is investigated. Further, the in situ conversion of the metallic tungsten into thin stoichiometric WS2 is achieved by a cyclic approach based on WF6 and H2S pulses at the moderate temperature of 450 °C, which is much lower than usual oxide sulfurization processes. ispartof: Journal of Materials Chemistry C vol:6 issue:15 pages:4122-4130 status: published

Epitaxial Si-O superlattices consist of alternating periods of crystalline Si layers and atomic layers of oxygen (O) with interesting electronic and optical properties. To understand the fundamentals of Si epitaxy on O atomic layers, we investigate the O surface species that can allow epitaxial Si chemical vapor deposition using silane. The surface reaction of ozone on H-terminated Si(100) is used for the O deposition. The oxygen content is controlled precisely at and near the atomic layer level and has a critical impact on the subsequent Si deposition. There exists only a small window of O-contents, i.e. 0.7–0.9 atomic layers, for which the epitaxial deposition of Si can be realized. At these low O-contents, the O atoms are incorporated in the Si-Si dimers or back bonds (-OSiH), with the surface Si atoms mainly in the 1+ oxidation state, as indicated by infrared spectroscopy. This surface enables epitaxial seeding of Si. For O-contents higher than one atomic layer, the additional O atoms are incorporated in the Si-Si back bonds as well as in the Si-H bonds, where hydroxyl groups (-Si-OH) are created. In this case, the Si deposition thereon becomes completely amorphous.

The structure, crystallinity and properties of as-deposited two-dimensional (2D) transition metal dichalcogenides are determined by nucleation mechanisms in the deposition process. 2D materials grown by atomic layer deposition (ALD) in absence of a template, are polycrystalline or amorphous. Little is known about their nucleation mechanisms. Therefore, we investigate the nucleation behavior of WS2 during plasma enhanced ALD from WF6, H2 plasma and H2S at 300 °C on amorphous ALD Al2O3 starting surface and on monocrystalline, bulk sapphire. Preferential interaction of the precursors with the Al2O3 starting surface promotes fast closure of the WS2 layer. The WS2 layers are fully continuous at WS2 content corresponding to only 1.2 WS2 monolayers. On amorphous Al2O3, (0002) textured and polycrystalline WS2 layers form with grain size of 5 nm to 20 nm due to high nucleation density (~1014 nuclei/cm2). The WS2 growth mode changes from 2D (layer-by-layer) growth on the initial Al2O3 surface to three-dimensional (Volmer-Weber) growth after WS2 layer closure. Further growth proceeds from both WS2 basal planes in register with the underlying WS2 grain, and from or over grain boundaries of the underlying WS2 layer with different in-plane orientation. In contrast, on monocrystalline sapphire, WS2 crystal grains can locally align along a preferred in-plane orientation. Epitaxial seeding occurs locally albeit a large portion of crystals remain randomly oriented, presumably due to the low deposition temperature. The WS2 sheet resistance is 168 MΩµm suggesting that charge transport in the WS2 layers is limited by grain boundaries. ispartof: Journal of Vacuum Science & Technology A, Vacuum, Surfaces and Films vol:36 issue:1 pages:1-11 status: published

The synthesis of nickel silicide thin films via a vapor–solid reaction has been studied by exposing thin (10 nm) Ni films to silane (SiH4). The crystalline phases, the Ni/Si stoichiometric ratios, as well as the surface and interface properties of the resulting silicide films were investigated as a function of the growth parameters such as the SiH4 partial pressure, the reaction temperature, and the exposure time. At low temperature (300 °C), SiH4 exposure led to the self-limiting deposition of Si on Ni by catalytic decomposition of SiH4 but not to silicate formation. Between 350 and 400 °C, phase pure orthorhombic NiSi films were obtained that were formed directly without any apparent intermediate Ni-rich silicide phases. A transformation to NiSi2 occurred at 450 °C and above, and at 500 °C phase pure NiSi2 was obtained. Here, the transient formation of NiSi was observed that transformed into NiSi2 for prolonged SiH4 exposure. The results indicate that the Si solubility governs the phase formation sequen...

Nanoscale morphology of vanadium dioxide (VO2) films can be controlled to realize smooth ultrathin (

Rutherford backscattering and channeling spectrometry (RBS/C) as well as transmission electron microscopy (TEM) are used to characterize the crystalline structure of a GaN layer grown on a Si (1 1 1) substrate. The channeling measurements are performed along the off-normal 〈 1 2 ¯ 1 3 〉 axis in the { 1 0 1 ¯ 0 } plane of the GaN layer. The threading edge dislocation defect density obtained from RBS/C is quantitatively compared to the results obtained from TEM. The strain is found not to be completely relaxed, eT ≠ 0, in spite of the large thickness of the GaN layer (3.0 μm), and in spite of the incorporation of various buffer layers.

Self-assembled monolayers (SAMs) derived from 11-cyanoundecyltrichlorosilane precursor are deposited in vapor phase and characterized on ultra-low- k Chemical Vapor Deposition (CVD) dielectric films ( k = 2.0) with open porosity up to 50% and pore diameter as large as 3.5 nm. Two surface preparation methods, such as Ar/H 2 and Ar/N 2 plasma pretreatments, are investigated and the pore sealing efficiency after SAM deposition is quantified from the experimental determination of open porosity and pore size measurements derived from toluene adsorption isotherms. In parallel, low- k damage is evaluated after surface preparation and SAM deposition by XPS depth profiling and by monitoring the change in refractive index, thickness and k value together with the –CH 3 and –CH 2 normalized FTIR peak areas vs. the pristine dielectric. Subsequently, a 10 nm HfO 2 thin film was deposited by Atomic Layer Deposition (ALD) in order to assess the pore-sealing capability of the proposed approach. When combining surface activation, SAM deposition and ALD, it was possible to accomplish a wide range of pore sealing. By adequate optimization, it was possible to obtain complete pore sealing after ALD, without precursor penetration into the porous low- k film, but at the expense of a 37% k increase for a 90 nm dielectric thickness.