TiAlN coatings with different modulation ratios were prepared on 42CrMo4 steel by hybrid multiarc ion plating and high-power impulse magnetron sputtering (HiPIMS). As the HiPIMS fraction increased, the coating surface showed fewer macroparticle-related defects and the cross-sectional structure became more uniform and compact. XRD analysis indicated that all coatings were mainly composed of face-centered cubic (Ti,Al)N with a weak AlN peak, while a slight shift of the (111) peak and an increase in the (200) reflection suggested a modulation-ratio-dependent evolution in texture and structural state. Among the alternating coatings, the critical load (LC2) increased from 22 to 47 N and the wear rate decreased from 4.95 & times; 10(-4) to 2.60 & times; 10(-4) mu m(3)& sdot;(N mu m)(-1) as the modulation ratio increased from 1:0.5 to 1:2. Electrochemical tests showed that the 1:2 coating exhibited the lowest corrosion current density, the highest polarization resistance, and the largest capacitive arc radius, indicating the best overall corrosion resistance among the alternating coatings. Overall, increasing the HiPIMS contribution effectively improved the comprehensive performance of the alternating TiAlN coatings.
This study introduces a novel two-step approach for fabricating high-performance transparent conducting films. The method involves depositing a highly conductive flat indium tin oxide (ITO) base layer via magnetron sputtering under conventional conditions, followed by a top layer of ITO nanowires deposited by magnetron sputtering without oxygen in the process gas. We demonstrate that this architecture synergistically combines the low sheet resistance of the dense base layer with the antireflective properties of the nanowire layer, resulting in enhanced light transmittance. Crucially, the predeposited ITO layer significantly facilitates nanowire nucleation, enabling their growth at reduced temperatures compared to direct deposition on bare glass. Sputtering on bare glass and ITO-precoated substrates at temperatures ranging from 200 to 550 degrees C was used to elucidate substrate- and temperature-dependent growth mechanisms. Energy-dispersive x-ray mapping demonstrated substrate-dependent tin depletion in nanowire bodies and pronounced tin segregation at nanowire tips, governed by diffusion dynamics. Furthermore, the nanostructured surface imparts tunable wettability, transitioning from hydrophilic on bare glass to highly hydrophobic, with contact angles as high as
Achieving and maintaining ultraclean vacuum environments is critical for contamination-sensitive processes such as semiconductor manufacturing, where residual gases directly affect performance and reproducibility. During pump-down, H2O outgassing from ambient-exposed technical materials often dominates the gas load, yet energetics-resolved studies of H2O release from these materials remain limited compared with ideal, single-crystal surfaces. In this work, ultrahigh-vacuum temperature-programmed desorption (TPD) was used to investigate H2O outgassing from Mo, 304 stainless steel, 6061 aluminum, Macor, and Si3N4 following exposure to 50% relative humidity (RH) at 20 degrees C. TPD spectra quantified retained H2O and enabled the extraction of apparent desorption-energy distributions. Coupling these distributions to a surface "sojourn-time" model translated TPD-derived energetics into effective release timescales, identifying which energetic states dominate gas load at a given temperature and how elevated bakeout temperatures accelerate H2O desorption. Molybdenum desorbed 1.5-3.7 monolayer equivalents of H2O over a broad range (similar to 50-650 degrees C) for exposure times from 15 min to 480 h with recurring desorption features embedded within a broad similar to 90-260 kJ/mol apparent desorption-energy envelope. X-ray and ultraviolet photoelectron spectroscopy measurements showed that ambient exposure forms a hydroxylated, MoO3-rich surface that progressively dehydrates and reduces to a metallic state during heating. Applying the same protocol to other materials revealed strongly material-dependent H2O retention. After 20 h at 50% RH, Mo, 304 SS, and Si3N4 released similar to 1-3 monolayers of H2O, whereas 6061 aluminum and Macor released substantially larger amounts at lower temperatures (<200 degrees C). These measured inventories and desorption-energy distributions provide a quantitative basis for comparing vacuum materials and optimizing pump-down and bakeout strategies.
CoFeB is a critical ferromagnetic material in magnetic tunnel junctions (MTJs), the fundamental components of magnetic random access memory (MRAM) devices. The precise control of CoFeB’s etching behavior is essential for optimizing MTJ performance. In this study, the etching characteristics of CoFeB magnetic nanofilms were examined using an inductively coupled plasma reactive ion etching (ICP-RIE) system with Ar, CO/Ar, and SF6/Ar plasmas. AR-N photoresist was employed as the etching mask to investigate the effects of ICP power, radio frequency (RF) bias power, and chamber pressure on both the etching rate and the resulting morphology. Our findings demonstrate that effective etching of CoFeB can be achieved using pure Ar plasma. Additionally, optimizing power and pressure parameters improves the etching selectivity between the CoFeB nanofilm and the photoresist. However, after physical etching with pure Ar, significant redeposition was observed, leading to an increase in the nanopillar diameter. The introduction of CO or SF6 into the Ar plasma resulted in a marked reduction in the etching rate of CoFeB. Additionally, etching experiments conducted on different overlayer-substrate thin film combinations revealed notable differences in both etching rates and morphology.
In advanced semiconductor manufacturing, achieving ultrahigh ashing uniformity is critical. This study systematically investigated the combined effects of the total gas flow rate and nitrogen addition in an inductively coupled plasma ashing process. A two-dimensional axisymmetric fluid model was integrated with experimental diagnostics. The results revealed that within a flow rate range of 200-1000 SCCM, the expanding separation vortex and enhanced convective transport synergistically homogenized the spatial distribution of reactive species, resulting in uniform ashing across the wafer. Furthermore, the performance improvement observed with the 10% N-2 addition is primarily driven by the "NO poisoning," which suppresses O atom loss at the surface through a marked significance in the sticking coefficient. This mechanism effectively resolves the conventional trade-off between the ashing rate and uniformity. An optimized process window of 500-1000 SCCM with 10% N-2 consistently delivered a high ashing rate (>500 nm/min) and excellent within-wafer uniformity (<3%).
Silicon nanowire field emitters were fabricated on top of microtubes on a silicon chip (dimensions including contact pads: 8 & times; 8 mm). There are 2437 microtubes (diameter: 8 mu m, height: 30 mu m, spacing: 40 mu m) in the array over an area of 3.38 mm(2). A process was developed to create an integrated metal gate for the extraction electrode. This involved coating the emitters with a uniform benzocyclobutene layer and fabricating a titanium/nickel extraction gate using lift-off. A plasma etching process was used to selectively remove the benzocyclobutene anisotropically around the microtubes, ensuring the preservation of the emitters and the extraction gate. The design reduces the capacitance between the cathode and gate and maximizes the length of the leakage paths between the cathode and gate. This reduces the overall risk of discharges between the two electrodes as well as the energy stored in the system for a given extraction voltage. The electron sources demonstrated transmission rates exceeding 96%, with currents reaching 0.4 mA at extraction voltages of 250 V for several hours under voltage-controlled operation. Investigations after the measurements showed that isolated discharges destroyed individual emitters during operation, but the electron sources remained functional. Consequently, these cathodes demonstrated resilience to failure caused by discharge-related damage due to the low capacity of the system. At higher voltages (300 V) and currents (2 mA); however, these samples exhibited catastrophic arcing, as at these voltages, the energy stored in the capacitance was large enough to result in the destruction of larger areas of the arrays and the formation of conductive paths between the cathode and the gate.
We introduce the new simulation tool ContaminationFlow, a test-particle Monte-Carlo (TPMC) simulator to predict the spread of contamination in vacuum environments with a view to virtual prototyping of space vehicles and earth bound vacuum applications. The paper comprises a description of the TPMC method for transient particle transport simulations under molecular flow conditions and for long-term investigations up to several years, which is illustrated by a benchmark problem. The implemented physical models are described along with the simulation algorithm. Strengths and weaknesses of the software are evaluated as well as future measures with regard to the improvement of the prediction accuracy are pointed out.
Failure analysis is essential for semiconductor technology development, manufacturing yield improvement, and long-term product reliability. As device dimensions continue to shrink into the single-digit nanometer regime, traditional optics-based global fault isolation (GFI) techniques—such as lock-in thermography, photon emission microscopy, optical beam-induced resistance change, thermally induced voltage alteration, critical parameter analysis, and laser voltage imaging/probing—are increasingly limited by the diffraction limit of light and can no longer precisely localize defects in dense 3D structures, including FinFETs and gate-all-around (GAA) nanosheet devices. Consequently, semiconductor failure analysis now relies heavily on SEM-based local fault isolation techniques, including nanoprobing, active voltage contrast, electron beam absorption current, electron beam induced current, and electron beam induced resistance change, which offer true nanoscale spatial resolution. However, these SEM-based techniques are only suitable to investigate a small area, which need be priorly narrowed down by GFI. This article evaluates the strengths and limitations of both optics-based and SEM-based techniques and presents case studies showing how combining these complementary techniques enables faster, more efficient, and more accurate defect localization in advanced 2 nm GAA nanosheet devices.
At various spinning speeds, Y2O3:Ho3+, Yb3+ thin films were grown on quartz substrates through a sol-gel spin coating route. High-temperature treatment of the deposited films was further done at 1000 degrees C. The structural and surface properties of the films were explored using powder x-ray diffraction (PXRD) and x-ray photoelectron spectroscopy (XPS). The thicknesses of the thin films were estimated using XPS depth profiles and the Swanepoel method. The structural analysis revealed a mixture of SiO2 and Y2O3 phases. The XPS high-resolution scans and depth profiles confirmed that the extra SiO2 phase resulted from the diffusion of the quartz substrate's elements into the prepared films due to high-temperature treatment. The films' thicknesses decreased with increasing spinning speed. Upon 448 nm excitation, the films showed a dominant near-infrared emission at 1204 nm assigned to the I-5(6) -> I-5(8) transition of the Ho3+ ion, with no trace of Yb3+ emission. The results revealed that the near-infrared (NIR) emission intensity of the films was dependent on the spinning speed. The spinning speed influenced surface roughness and film thickness, which, in turn, affected NIR emission via total internal reflection and excitation volume. The improved emission at 1204 nm indicates that the Y2O3:Ho3+, Yb3+ films are suitable for laser applications, among other fields.
Thermionic cathodes are central to plasma and vacuum devices, where emission efficiency, sheath coupling, and thermal robustness strongly influence performance and lifetime. Hybrid cathodes that integrate carbon nanotubes (CNTs) with low-work-function oxides have demonstrated enhanced thermionic emission in vacuum, but their behavior in plasma environments remains largely unexplored. Here, a Ba-Sr-O-coated CNT thermionic cathode is investigated in a low-pressure Ar-Hg glow discharge plasma and directly compared with a conventional Ba-Sr-Ca (BSC) oxide cathode fabricated on identical triple-coiled tungsten filaments. In vacuum, the Ba-Sr-O-CNT cathode delivers 3-4 times higher emission current than the BSC cathode at comparable temperature and electric field, despite exhibiting a higher work function (1.6 vs 1.3 eV), indicating strong CNT-induced Schottky field enhancement. In plasma operation, cathode fall voltages are measured using a capacitive band probe, and cathode surface temperatures are simultaneously determined by optical pyrometry over a range of discharge and auxiliary heating currents. Under all tested conditions, the Ba-Sr-O-CNT cathode exhibits substantially lower peak cathode fall (9.8-14.6 V), and hotspot temperatures reduced by 70-80 degrees C relative to the conventional cathode at the same discharge current. These cathode fall values place the CNT cathode below the similar to 16 V threshold commonly associated with excess ion sputtering in Ar-Hg plasmas, whereas the conventional cathode operates near or above this limit. The results demonstrate that CNT-enabled emission enhancement persists in plasma, reducing sheath potential and thermal loading and suggesting improved resistance to sputtering-induced degradation.
Gas-surface scattering kernels used in rarefied flow and vacuum modeling commonly assume Maxwellian reflection with constant accommodation coefficients. Molecular dynamics simulations were performed to quantify Ar scattering from a thermostated Pt(100) surface using a molecular-beam configuration. Incident speeds spanning 0.5-8 times the most probable speed and incident angles of 5 degrees, 45 degrees, and 75 degrees were considered. Three trajectory classes were observed: single-bounce reflection, multibounce reflection, and adsorption following multiple bounces. Escape from the surface potential well occurred when the peak normal momentum during the interaction exceeded the incident normal momentum. Reflected velocity distributions were strongly non-Maxwellian. At low incident speeds, the tangential component was well described by a Gaussian and the normal component lay between Maxwellian and Gaussian forms. With increasing incident speed, the tangential distribution developed a shoulder and ultimately became bimodal, accompanied by tangential-normal coupling. Increasing incident angle reduced the spread of reflected velocities and shifted scattering from diffuse toward specularlike reflection. Accommodation coefficients were markedly condition dependent: tangential momentum accommodation decreased monotonically with incident speed at large angles; normal momentum and energy accommodation exhibited opposite trends between low- and high-speed regimes; and tangential momentum accommodation exceeded unity at small angles, indicating tangential velocity reversal. Motivated by the low-speed behavior, a tangential scattering-kernel parameterization is proposed in which a Gaussian distribution is used with incident-speed- and angle-dependent mean and variance, providing a compact model form for gas-surface boundary conditions.
In the post-Moore era, conventional solid-state electronic devices face increasing limitations in high-frequency operation. Although traditional vacuum electronic devices offer excellent high-frequency and high-power capability, their large size makes them incompatible with modern requirements for miniaturization and integration. This work explores a micro-/nanoscale vacuum electronic device based on a gallium nitride vacuum field-emission diode with a vertical structure. A fabrication process compatible with conventional photolithography, plasma-enhanced atomic layer deposition, and reactive ion etching is developed, avoiding the use of costly electron-beam lithography. Electrical measurements under different ambient conditions demonstrate stable field-emission behavior. In atmospheric measurements, the device delivers current in the order of hundreds of mu A at 5 V, while under high vacuum (10(-5) Pa), the output current increases to about 10 mA at the same bias. To describe the device behavior, a symbolically defined device model and a small-signal equivalent circuit model are established. Based on the extracted nonlinear field-emission resistance and capacitance terms, the RF potential of the device is analyzed using an RC-based framework. The analysis further separates the intrinsic and extrinsic capacitance contributions, showing that the local emission region can in principle support a much higher intrinsic cutoff frequency limit than that of the present full device structure. The overall high-frequency performance is found to be mainly limited by parasitic capacitance associated with the surrounding macroscopic layout. These results provide both a device platform and a modeling framework for the further optimization of GaN-based vacuum nanoelectronic devices toward high-frequency applications.
High-resolution x-ray imaging under low-voltage conditions is essential for nondestructive evaluation of lithium-ion batteries, where microscale internal defects critically affect safety and long-term performance. However, many previously reported electron emission sources exhibit limitations in beam confinement, particularly under low-voltage or high-current operating conditions, which can restrict imaging resolution and practical applicability. To address these challenges, a newly optimized single-island C-beam x-ray source based on a carbon nanotube (CNT) cold-cathode field emitter is proposed for low-voltage, high-resolution battery inspection. The electron source was optimized through improved electrode geometry and electrostatic focusing, resulting in enhanced beam convergence and reduced focal spot size. Electrical characterization demonstrated reliable operation, delivering a maximum emission current of 1.15 mA in a diode mode and a stable anode current of 0.42 mA in a triode mode. These improvements enabled the formation of a tightly confined focal spot of approximately 32 mu m at an anode voltage of 65 kV. Imaging performance was quantitatively validated using line-pair phantoms, confirming a practical spatial resolution of 38.5 mu m with contrast-to-noise ratio values ranging from 1.6 to 5.47 under low-dose conditions. The optimized system further achieved high-throughput capability, supporting inspection rates of 300-500 cylindrical cells/min, surpassing conventional low-voltage commercial x-ray systems. The proposed CNT-based C-beam source demonstrates a compact, energy-efficient, and scalable solution for rapid, low-dose, and high-fidelity nondestructive inspection of advanced energy storage devices.
Liquid atomization is a key factor in inhalation therapy because it determines where inhaled aerosols deposit within the respiratory tract. Delivery to the deep lung generally requires aerosol generation in the range of 1-5 mu m. However, current medical nebulizers often struggle to produce aerosols in this size range at high yield and tend to generate an undesirable coarse aerosol fraction. In mesh nebulizers, which are compact, quiet, and increasingly used in clinical settings, the nozzle-aperture diameter governs the resulting aerosol size. In this study, we fabricated nozzle-array filters with submicrometer-to-few-micrometer apertures-which are difficult to realize via conventional methods-using multistep exposure x-ray lithography, and demonstrated high-yield generation of 1-5 mu m aerosols with a mesh nebulizer. We fabricated filters with mean aperture diameters of 7.5, 2.3, and 1.6 mu m at NewSUBARU BL11 and evaluated them using a commercial piezoelectric oscillator unit. Laser diffraction measurements showed that the median aerosol diameter decreased systematically with aperture diameter, from 12.5 to 4.8 and 3.2 mu m, with the smallest-aperture filter producing aerosols predominantly within the target 1-5 mu m range for inhalation therapy. We also examined the dependence of nebulization performance on liquid properties and confirmed stable aerosol generation within the 1-5 mu m range for a clinically relevant aqueous formulation. These results establish a practical route to 1-5 mu m aerosol generation through aperture-controlled nozzle-array design and x-ray lithography-based fabrication.
Three-dimensional electron energy-loss spectroscopy (EELS) has long been recognized as a promising technique for the chemical mapping of nanoscale devices; however, its spatial resolution has historically been constrained. In this study, we demonstrate subnanometer resolution in EELS tomography, enabling the precise identification of chemical defects within a fin field-effect transistor (finFET) structure. The finFET specimens were fabricated into <50 nm diameter needle-shaped geometries using focused ion beam milling to facilitate a full 180 degrees tilt series of scanning transmission electron microscopy EELS spectrum images. To overcome severe carbon contamination and low signal-to-noise ratios, we employed a structurally validated background subtraction method paired with multivariate statistical analysis for robust denoising. Three-dimensional chemical maps were subsequently computed using the generalized Fourier iterative reconstruction algorithm. The resulting tomograms successfully resolve a localized similar to 0.79 nm oxide defect resulting from oxygen incorporation within the TaN metal gate. Furthermore, by evaluating the reconstructions via Fourier shell correlation using the 1/2-bit information criterion, we demonstrate that a spatial resolution of 0.87 nm is achievable even under a 50% reduced electron dose. These findings establish a reliable EELS tomographic workflow for investigating buried, subnanometer chemical inhomogeneities in advanced semiconductor architectures.
Hybrid bonding involves simultaneously bonding of two different materials, viz., interlayer dielectric film (ILD)-ILD and Cu-Cu. This process requires the simultaneous involvement of two distinct bonding mechanisms with different participating functional groups and requires high bonding energy as well as an oxide-free Cu-Cu bonding interface. In hybrid bonding, hydrophilic groups are formed at the bonding interface to achieve ILD bonding. This inevitably forms Cu oxide on the Cu surface at the bonding interface. To address this issue, a plasma chamber equipped with a low-inductance antenna (LIA) was utilized in our previous study, enabling to achieve Cu-Cu direct bonding at low temperatures. In this study, sequential ArH2 and ArH2N2 plasma-assisted activation using an LIA enables the termination of a higher density of hydrophilic groups, which serve as bonding groups in ILD bonding, thereby achieving high bonding energy at temperatures <200 degrees C. This new surface-activation method for hybrid bonding enables simultaneous bonding of the ILD-ILD film and Cu-Cu at a postannealing temperature significantly lower than that required for conventional hydrophilic bonding. Furthermore, high bonding energy and good bonding quality can be achieved without forming an oxide film on the Cu-Cu bonding interface, thus overcoming a major limitation associated with low-temperature hydrophilic bonding. These features enable significant lowering of the postannealing temperature in hybrid bonding, thereby enabling the fabrication of highly integrated devices for future three-dimensional device technology.
High-aspect-ratio contact (HARC) SiO2 etching at ultralow pressure offers fundamental advantages in ion transport but has been difficult to implement in practice due to plasma instability and limited etch rates in conventional capacitively coupled plasma systems. In this work, a stable HARC SiO2 etching process is demonstrated at an ultralow pressure of 3 mTorr using an inductively coupled plasma (ICP) system. The complementary roles of low-frequency bias power and ICP source power are systematically investigated. Increasing the bias power enhances ion-energy-driven surface reactions, resulting in a monotonic increase in the SiO2 etch rate while maintaining stable SiO2/amorphous carbon layer selectivity. In contrast, increasing the source power increases plasma density and reactive flux, leading to a substantial etch-rate enhancement without degrading profile anisotropy. As a result, SiO2 etch rates of approximately 190 nm/min are achieved with vertical sidewalls and acceptable mask selectivity. These results demonstrate that ultralow-pressure ICP operation provides a practical and robust route for advanced HARC SiO2 etching.
Semiconducting two-dimensional materials, such as the transition metal dichalcogenides (TMDs), are atomically thin with desirable bandgaps that make them highly applicable for aggressively scaled transistors. However, it has proven challenging to achieve reproducible, high-quality metal-semiconductor contact interfaces to TMDs. Past work has employed intentional TMD crystal damage prior to contact metallization to improve the metal-semiconductor interface, but such an approach has not been studied for tungsten-based TMDs (W-TMDs), which are resistant to most standard etching techniques. In this study, we use an Ar ion beam to parametrically investigate the etching effect of ion energy and exposure time on mechanically exfoliated WSe2. Results indicate that 300 eV Ar ion bombardment provides sufficient energy to modify WSe2 without complete destruction of the crystal lattice, supported by atomic force microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. This Ar ion beam exposure is then applied to modify the contact region of WSe2 field-effect transistors via exposure immediately prior to in situ metal deposition. Compared to the unexposed devices, the devices with contact regions exposed to the ion beam demonstrate a minor reduction in device on-current; however, a 3 s ion beam exposure reveals a surprising improvement in standard deviation of on-current across a set of devices from 5.42 down to 0.77 mu A/mu m. This study provides a basis for future W-TMD processing and a potential route for improving TMD field-effect transistor variability through contact region modifications.
In this article, we focus on the impact of ammonia flow rate during metal-organic chemical vapor deposition growth on the luminescence characteristics of InGaN multiple quantum wells (MQWs). By analyzing the electroluminescence spectra, temperature-dependent photoluminescence, and fluorescent microscopy images of MQW light-emitting diodes, we established the influence of ammonia flow rate on nonradiative recombination centers and localized states appearing on the surface and inside quantum wells. It was found that the ammonia flow rate affects the distribution of localized states in the bulk of quantum wells, reducing the FWHM of luminescence peaks. In addition, increasing the ammonia flow rate promotes the surface decomposition of InGaN films and decreases growth rate, weakening the quantum-confined Stark effect and improving surface quality. But it also makes injected carriers more susceptible to be captured by nonradiative recombination centers, which may reduce luminescence efficiency.
Two-dimensional (2D) materials have emerged as promising candidates for next-generation semiconductors owing to their superior electrical and mechanical characteristics. However, conventional synthesis methods, such as chemical vapor deposition and mechanical exfoliation, face challenges in achieving the large-area scalability and efficiency required for high-performance logic devices. To address these issues, this study demonstrates a scalable manufacturing process utilizing electrochemical exfoliation. This cost-effective solution-based method facilitates the production of high-quality 2D nanosheets by weakening the interlayer van der Waals forces of bulk crystals. The resulting n-type MoS2 and p-type WSe2 inks were uniformly deposited via a large-area blade coating technique. To mitigate defects generated during exfoliation, we employed a chemical passivation treatment using bis(trifluoromethane)sulfonimide (TFSI). The fabricated MoS2 and WSe2 thin-film transistors exhibited enhanced electrical performance, with significant improvements in carrier mobility (up to 10 and 5 cm(2) V-1 s(-1), respectively) and on/off current ratios (exceeding 10(5)). Furthermore, by integrating these optimized n-type and p-type channel devices, we successfully demonstrated functional CMOS inverter logic circuits with a gain of similar to 6. These results suggest that combining electrochemical exfoliation, defect engineering via TFSI, and blade coating offers a viable pathway for realizing large-scale 2D integrated circuits.
