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Surface terminations profoundly influence the intrinsic properties of MXenes, but existing terminations are limited to monoatomic layers or simple groups, showing disordered arrangements and inferior stability. Here we present the synthesis of MXenes with triatomic-layer borate polyanion terminations (OBO terminations) through a flux-assisted eutectic molten etching approach. During the synthesis, Lewis acidic salts act as the etching agent to obtain the MXene backbone, while borax generates BO2−species, which cap the MXene surface with an O–B–O configuration. In contrast to conventional chlorine/oxygen-terminated Nb2C with localized charge transport, OBO-terminated Nb2C features band transport described by the Drude model, exhibiting a 15-fold increase in electrical conductivity and a 10-fold improvement in charge mobility at the d.c. limit. This transition is attributed to surface ordering that effectively mitigates charge carrier backscattering and trapping. Additionally, OBO terminations provide Ti3C2MXene with substantially enriched Li+-hosting sites and thereby a large charge-storage capacity of 420 mAh g−1. Our findings illustrate the potential of intricate termination configurations in MXenes and their applications for (opto)electronics and energy storage.

High-resolution nano X-ray computed tomography (nano-XCT) was used to investigate the process of infiltration of a Molten Carbonate Fuel Cell (MCFC) matrix by liquid electrolyte. A ceramic matrix made of a LiAl 2O3powder was infiltrated by a liquid electrolyte during the start-up process of the MCFC. Nano-XCT extends the state-of-the art techniques for characterizing the morphology of the ceramic matrix and for the study of the penetration kinetics with electrolyte. Quantitative morphology analysis using high-resolution nano-XCT provides 3D information for each MCFC component nondestructively. The spatially resolved volume fraction of the molten electrolyte calculated from the 3D XCT data is used for simulation and to improve MCFC performance. Based on the results obtained, a new start-up procedure is proposed for a single MCFC. This procedure is consistent with the morphology changes which occur during the melting process inside the ceramic matrix.

Quasi-two-dimensional (q2D) conducting polymer thin film synergizes the advantageous features of long-range molecular ordering and high intrinsic conductivity, which are promising for flexible thin film-based micro-supercapacitors (MSCs). Herein, we present the high-performance flexible MSCs based on highly ordered quasi-two-dimensional polyaniline (q2D-PANI) thin film using surfactant monolayer assisted interfacial synthesis (SMAIS). Owing to high electrical conductivity, rich redox chemistry, and thin-film morphology, the q2D-PANI MSCs show high volumetric specific capacitance (ca. 360 F/cm3) and energy density (17.9 mWh/cm3), which outperform the state-of-art PANI thin-film based MSCs and promise for future flexible electronics.

Both in situ microscopy experiments at embedded inlaid copper interconnect structures and numerical simulations based on a physical model provide information about electromigration-induced degradation mechanisms in on-chip interconnects. It is shown that the modification of the bonding strength of the weakest interface results in completely changed degradation and failure mechanisms. Transmission electron microscopy (TEM) images of standard Cu/SiNxinterfaces are compared with strengthened interfaces, e. g., after applying an additional metal coating or a self-assembled monolayer (SAM) on top of the polished copper lines. The changed degradation mechanisms as observed with the in situ scanning electron microscopy (SEM) experiment and as predicted based on the numerical simulations are explained based on TEM images.

The atomic transport processes which could cause degradation mechanisms in Cu interconnects are described. The influence of interconnect line width, barrier type and anneal process on the microstructure and reliability of the inlaid Cu lines are discussed. Grain size and texture measurements have been performed at blanket films and at arrays of Cu lines using advanced analytical techniques. The median grain size decreases with decreasing line width, and it can be influenced by heat treatments. The crystallographic texture is predominantly {111} out-of-plane with sidewall-oriented grains in narrow Cu lines. The grains have an in-plane preferred orientation with the 〈110〉 direction parallel to the sidewall normal. The Cu texture is influenced by barrier structure and thickness.

The electrochemical N2reduction reaction (NRR) under ambient conditions is attractive in replacing the current Haber-Bosch process toward sustainable ammonia production. Metal-heteroatom-doped carbon-rich materials have emerged as the most promising NRR electrocatalysts. However, simultaneously boosting their NRR activity and selectivity remains a grand challenge, while the principle for precisely tailoring the active sites has been elusive. Herein, we report the first case of crystalline two-dimensional conjugated covalent organic frameworks (2D c-COFs) incorporated with M–N4–C centers as novel, defined, and effective catalysts, achieving simultaneously enhanced activity and selectivity of electrocatalytic NRR to ammonia. Such 2D c-COFs are synthesized based on metal-phthalocyanine (M = Fe, Co, Ni, Mn, Zn, and Cu) and pyrene units bonded by pyrazine linkages. Significantly, the 2D c-COFs with Fe–N4–C center exhibit higher ammonia yield rate (33.6 μg h–1mgcat–1) and Faradaic efficiency (FE, 31.9%) at −0.1 V vs reversible hydrogen electrode than those with other M–N4–C centers, making them among the best NRR electrocatalysts (yield rate >30 μg h–1mgcat–1and FE > 30%). In situ X-ray absorption spectroscopy, Raman spectroelectrochemistry, and theoretical calculations unveil that Fe–N4–C centers act as catalytic sites. They show a unique electronic structure with localized electronic states at Fermi level, allowing for stronger interaction with N2and thus faster N2activation and NRR kinetics than other M–N4–C centers. Our work opens the possibility of developing metal–nitrogen-doped carbon-rich 2D c-COFs as superior NRR electrocatalyst and provides an atomic understanding of the NRR process on M–Nx–C based electrocatalysts for designing high-performance NRR catalysts.

The proton-exchange-membrane (PEM) water-splitting electrolyser is a highly appealing technology for economical hydrogen production. Unfortunately, only Iridium (Ir)-based electrocatalysts show efficient and stable activity towards oxygen evolution reaction (OER) in acidic medium, which seriously hampers the large-scale utilization of PEM water splitting electrolyser as a result of high cost and scarcity of the Ir. Here, we report synthesis of Ir nanoparticles on 3D graphite foam (Ir/GF) upon a heat treatment of Ir3+/polyaniline complex that were beforehand prepared on the GF. Benefiting from low content of Ir (5.91wt%) and excellent resistance of 3D graphite foam against oxidative corrosion, the resultant Ir/GF functionalizes as a novel bifunctional electrocatalyst for overall water splitting in a 0.5M H2SO4solution. Noticeably, the HER and OER overpotentials of the Ir/GF at 10mA/cm2are only ~ 7mV and ~ 290mV, respectively, which are much lower than those of commercial Pt/C and Ir/C catalysts as well as reported Pt or Ir-based electrocatalysts. Significantly, an acidic water-splitting electrolyser with a current density of 10mA/cm2is steadily driven by the Ir/GF at a cell voltage of only ~ 1.55V, which is substantially lower than 1.65V for commercial Pt/C and Ir/C couple.

Germanium is a promising material for future very large scale integration transistors, due to its superior hole mobility. However, germanium-based devices typically suffer from high reverse junction leakage due to the low band-gap energy of 0.66 eV and therefore are characterized by high static power dissipation. In this paper, we experimentally demonstrate a solution to suppress the off-state leakage in germanium nanowire Schottky barrier transistors. Thereto, a device layout with two independent gates is used to induce an additional energy barrier to the channel that blocks the undesired carrier type. In addition, the polarity of the same doping-free device can be dynamically switched between p- and n-type. The shown germanium nanowire approach is able to outperform previous polarity-controllable device concepts on other material systems in terms of threshold voltages and normalized on-currents. The dielectric and Schottky barrier interface properties of the device are analyzed in detail. Finite-element drift-diffusion simulations reveal that both leakage current suppression and polarity control can also be achieved at highly scaled geometries, providing solutions for future energy-efficient systems.

Due to the electronic and structural properties of silicon, silicon nanowires have a great potential in nanoscale electronic devices and sensors. Silicon nanowires used for reconfigurable field effect transistors are designed, synthesized and characterized after each step in order to ensure excellent electrical and physical properties of the end product and to study various process parameters. In this study, silicon nanowire based reconfigurable field effect transistors are studied as as-grown “forests”, individually, oxidized and after forming Schottky junctions. The analysis is performed using scanning electron microscopy and transmission electron microscopy. Focused ion beam based preparation was carried out in the case of samples with Schottky junctions. This paper provides a comprehensive description of sample preparation and characterization of the nanowires.

Managing the emerging internal mechanical stress in chips particularly if they are 3D-tscked is a key task to maintain performance and reliability of microelectronic products. Hence, a strong need of a physics-based simulation methodology/flow emerges. This physics-based simulation, however, requires materials parameters with high accuracy. A full-chip analysis can then be performed, balancing the need for local resolution and computing time. Therefore, effective composite-type materials data for several regions of interest are needed. Advanced techniques to measure FEA-and design-relevant properties such as local and effective Youngs modulus and effective CTE values were developed and described in this paper. These data show a clear orientation dependence, caused by the chip design.

Abstract

Abstract: We have studied the heat treatment influence (room temperature to 400°C) on thin aminopropyltrimethoxysilane (APTMS)-based films incorporated with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), copper phthalocyanine (CuPc), and three-dimensional structure cage polyhedral oligomeric silsesquioxanes (POSS) by X-ray photoelectron spectroscopy and capacitance voltage technique. We discuss the interplay between the temperature degradation of the organic components (aminopropyl groups, sp3-based carbon bonds of APTMS, cyclopentyl rings, and vinyl functional group of POSS) and the thermal stability of the fullerene molecules (PCBM), benzene rings (CuPc), and the POSS inorganic cages. We observe the formation of Si–O–Si bridges between the POSS inorganic cages and the SiO2-enriched matrix which contains also fullerene molecules and benzene rings.

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Abstract

Future nanoelectronics manufacturing at extraordinary length scales, new device structures, and advanced materials will provide challenges to process development and engineering but also to process control and physical failure analysis. Advanced X‐ray techniques, using lab systems and synchrotron radiation sources, will play a key role for the characterization of thin films, nanostructures, surfaces, and interfaces. The development of advanced X‐ray techniques and tools will reduce risk and time for the introduction of new technologies. Eventually, time‐to‐market for new products will be reduced by the timely implementation of the best techniques for process development and process control. The development and use of advanced methods at synchrotron radiation sources will be increasingly important, particularly for research and development in the field of advanced processes and new materials but also for the development of new X‐ray components and procedures. The application of advanced X‐ray techniques, in‐line, in out‐of‐fab analytical labs and at synchrotron radiation sources, for research, development, and manufacturing in the nanoelectronics industry is reviewed. The focus of this paper is on the study of nanoscale device and on‐chip interconnect materials, and materials for 3D IC integration as well.

Continuous scaling of Cu interconnect structures can significantly impact reliability-limiting processes such as electromigration and stress-induced voiding. Prior to the 65 nm technology node, mass transport under electromigration is dominated by diffusion along the Cu/dielectric cap interface and the electromigration lifetime will degrade by about half for every generation, even with the same current density. Beyond the 65 nm node, small grains were found to mix with bamboo grains in the 90 nm Cu damascene lines and the contribution of the grain boundary transport degraded the electromigration lifetime. The scaling effects on microstructure and electromigration reliability are examined in this paper with the objective of identifying the key issues and exploring potential solutions for sub-100 nm Cu interconnects. We discuss first the scaling effect on electromigration lifetime and the effect due to the small grains on electromigration lifetime and statistics. This is followed by a discussion on grain growth studies focusing on the formation of small grains and a recent simulation study on small grain effect on electromigration reliability. This paper concludes with a discussion of some recent developments in analytical techniques to investigate grain structure and electromigration reliability in sub-100 nm Cu lines.

We investigated in situ the atomic layer deposition is of the high‐kdielectric material HfO2. We used X‐ray photoelectron spectroscopy and ultra high vacuum atomic force microscopy for characterizing both the thin film and the substrate. With this technique, we determined the growth and the chemical‐physical properties of the thin film.

In semiconductor industry, process control and physical failure analysis were dominated by light and electron microscopy as well as surface analysis techniques including X-ray photoelectron spectroscopy (XPS) until the end of the last century. During the past decade, X-ray diffraction (XRD) and X-ray reflectivity (XRR) have been successfully applied in out-of-fab analytical labs. In addition to XRF and TXRF, some additional X-ray techniques - e.g. XRD, XRR and XPS - have been moved or are in the process to be moved from lab-based studies to in-line applications, using cleanroom compatible thin film characterization tools in wafer fabs. Lab-based smallangle X-ray scattering (SAXS) tools are applicable for pore size characterization in porous thin films. Advanced transmission X-ray microscopy (TXM) and X-ray computed tomography (XCT) systems with sub-100 nm resolution are currently being evaluated for their use in out-of-fab analytical labs. Apart from the on-site use of laboratory X-ray sources, synchrotron-radiation sources have been used in all fields of X-ray techniques: diffraction (SR-XRD), spectroscopy (SR-XPS, XAFS) and microscopy (SR-TXM/XCT). The high brightness and collimation of SR beams provide unique possibilities, e.g. for in-situ X-ray microdiffraction, photoelectron emission microscopy (PEEM) and in-situ TXM/XCT. In this paper, we demonstrate the high potential of the X-ray techniques for semiconductor industry, we describe potential implementations of these techniques for current and future applications, particularly for advanced process development and process monitoring, and we provide an outlook showing that we are living in a decade which is characterized by a breakthrough in the industrial application of Xray techniques. The application focus of this review is on the study of two types of nanostructures with typical dimensions less than 100 nm: artificial nanolayers and nanostructures caused by thin film deposition and patterning (litho/etch) processes as well as nanostructured materials, i. e. thin film materials with a “sub-structure” on sub-100 nm length scale.

The characterization of nanoscale regions in present and future device structures of leading-edge microelectronic products requires probes with dedicated features tailored on the nanoscale. SPM tips are used not only for conventional AFM characterization, but also for electrical, thermal and optical investigation of devices. For particular applications as nano-Raman spectroscopy or conductive AFM, highly reproducible metal tips or metallized tips are needed. In this paper, new approaches to tailor those tips using the FIB technique, and to characterize the tips using dedicated structures and adapted AFM methods are described. Based on a numerical procedure, the tip quality is described quantitatively. The described preparation and calibration techniques offer new possibilities for the routine application of nanostructures and nanodevices as needed for advanced SPM techniques and nanosensors.

In-situ SEM and XRM studies of fully embedded via/line interconnect structures allow imaging of the time-dependent void evolution in inlaid copper interconnects. It is shown that void formation, growth and movement, and consequently degradation, depend on interface bonding and copper microstructure. Specific experiments were designed to study reliability-limiting degradation mechanisms in on-chip interconnects. In this paper, the challenges of copper microstructure monitoring and the study of degradation mechanisms, related to the reliability of the copper inlaid structures, are discussed. In particular, in-situ experiments to visualize mass transport and degradation in fully embedded copper via/line test structures are described. A model for void formation, growth and movement, and consequently interconnect degradation, is proposed. Electromigration lifetime can be drastically increased by changing or modifying the copper/capping layer interface.

The microstructure of inlaid Cu lines has been quantified as a function of annealing conditions, post-plating, and post-CMP. The grain size distribution was measured using the median intercept method, crystallographic texture was characterized by pole figure analysis, and mechanical stress was determined using x-ray diffraction. The median grain size and mechanical stress level increase with increasing anneal temperature. The crystallographic texture is independent of the anneal temperature and is predominantly (111) with a small fraction of sidewall-nucleated (111) grains. The (111) grains nucleated from the trench bottom have a preferred in-plane orientation. The grain growth in the trench is independent of that in the overburden.

Die Charakterisierung von dünnen Schichten und Grenzflächen ist in der Halbleiterindustrie notwendig, um hohe Ausbeuten und die geforderte Zuverlässigkeit der Bauelemente zu sichern. Anforderungen an die Dünnschicht- und Grenzflächenanalytik werden besprochen und typische Anwendungen in der Halbleiterindustrie aufgezeigt. Charakteristische Eigenschaften dünner Schichten, die mit physikalischen Analysemethoden ermittelt werden müssen, sind Schichtgeometrie, Oberflächen- und Grenzflächenrauhigkeit, chemische Zusammensetzung und Gefüge. Die fortschreitende Verkleinerung der typischen Strukturgrößen in mikroelektronischen Bauelementen und der Einsatz neuer Materialien und Prozesse erfordern f r künftige Technologieniveaus Entwicklungen auf dem Gebiet physikalischer Untersuchungsmethoden. Um die Zeit zur Lösung von Problemen im Fertigungsprozess zu reduzieren, werden Gerätesysteme, die bisher nur in out-of-fab-Labors eingesetzt wurden, teilweise in sogenannte“at-line”-Labors verlagert werden, die nahe dem oder sogar im Reinraum gelegen sind.

Die Charakterisierung von dünnen Schichten und Grenzflächen ist in der Halbleiterindustrie notwendig, um hohe Ausbeuten und die geforderte Zuverlässigkeit der Bauelemente zu sichern. Anforderungen an die Dünnschicht‐ und Grenzflächenanalytik werden besprochen und typische Anwendungen in der Halbleiterindustrie aufgezeigt. Charakteristische Eigenschaften dünner Schichten, die mit physikalischen Analysemethoden ermittelt werden müssen, sind Schichtgeometrie, Oberflächen‐ und Grenzflächenrauhigkeit, chemische Zusammensetzung und Gefüge.

Amorphous Ni-Ta was obtained by mechanically alloying pure crystalline powders of nickel and tantalum. Structural changes in the local atomic arrangement effected by the mechanical treatment were studied by X-ray scattering and EXAFS spectroscopy. Both X-ray scattering and EXAFS data represent the destruction of long-range order with increasing milling time, i.e., the crystalline-to-amorphous transition. In contrast to an EXAFS study on the Ni-Ti system, our analysis does not confirm the presence of chemical short-range order.

The EXAFS amplitudes of concentrated samples measured in the fluorescence mode strongly depend on the detection geometry through the self-absorption effect. Knowing the stoichiometry of the sample, we can fully correct for the self-absorption effect using a simple theory and obtain the true EXAFS. The correction procedure presented here for the Oxygen K-edge EXAFS of NiO is generally applicable and should be the first step in the quantitative analysis of fluorescence EXAFS data of concentrated samples.

High quality fluorescence yield oxygen EXAFS spectra of Cu2O and CuO demonstrate the transferability of the O-Cu EXAFS phase-shift in contrast to earlier findings. This allows a precise O-Cu distance determination. It is shown for the copper oxides that theoretical calculations by means of the FEFF code yield reliable distance standards also in the soft x-ray region. These advances improve the distance determination by means of oxygen EXAFS and open up cases where reliable experimental standards are not available. Following a discussion of the oxygen EXAFS of NiO, the consequences with respect to the surface systems O/Cu and O/Ni are presented. In particular, a systematic error of +0.05Å in previous surface EXAFS distance determinations of O/Ni systems is established.

The Bayesian estimation method which is based on mathematical statistics combines experimental signals and pre-information in a common loss function. We have improved the original version of the Bayesian method and can take into account implicit constraints between the parameters of the EXAFS function, that must be fulfilled only within chosen error bounds. These linear relations connect occupation probabilities or phase fractions, coordination numbers, interatomic distances and mean-square relative displacements of the atoms.