Search Results (598)

Size-dependent efficiency degradation remains a major challenge for deeply scaled GaN-based micro-light-emitting diodes (micro-LEDs) because etched sidewalls increasingly influence carrier recombination. Here, square micro-LEDs with lateral dimensions of 5–50 μm were fabricated from the same plasma-assisted molecular-beam-epitaxy-grown wafer containing a five-period InGaN quantum-well/1 nm Al_0.1Ga_0.9N interlayer/InGaN quantum-dot-like (QW–QD) composite active region. Contrary to the conventional size effect, the light output power density and external quantum efficiency (EQE) increased as the mesa size decreased. The peak EQEs were 3.66%, 4.53%, 5.63%, 7.04%, and 7.27% for the 50, 40, 30, 10, and 5 μm devices, respectively, corresponding to an approximately 98.6% increase from 50 to 5 μm. The favorable scaling is consistent with localization-mediated suppression of lateral carrier loss combined with size-dependent light extraction. The present measurements do not quantitatively separate injection, internal efficiency, and extraction contributions. These results demonstrate the potential of ultrathin-interlayer QW–QD active-region engineering for scaled GaN micro-LEDs. Full article

Flexible pressure sensors serve as core sensing components for wearable health monitoring systems, electronic skins for soft robots, and flexible human–machine interaction devices. Benefiting from the interfacial electric double-layer polarization effect, iontronic sensing delivers far higher pressure response sensitivity than conventional parallel-plate capacitive sensors, endowing it with distinctive advantages in the detection of weak physiological signals. Nevertheless, current dense ionic thin-film dielectric layers suffer from limited deformation space under compression and poor low-pressure sensing capability. Mainstream high-precision micropillar arrays are fabricated via photolithography, 3D printing, and metal etching molds, which require costly equipment and complicated fabrication procedures, making large-area mass production unfeasible. Random frosted concave-convex microstructures feature disordered dimensions, leading to severe device hysteresis and narrow linear ranges, which fail to achieve ultrahigh sensitivity alongside a wide pressure detection range simultaneously. To address the aforementioned multiple bottlenecks, this paper proposes a low-cost resin template replication process to fabricate TPU-based ionic thin-film dielectric layers with ordered micropillar array microstructures. Combined with inkjet-printed silver conductive PI flexible electrodes, an iontronic flexible pressure sensor with a sandwich layered structure is constructed. Multi-dimensional investigations including microscopic morphology characterization, electromechanical sensing performance calibration, and human wearable application tests are systematically implemented to thoroughly elucidate the synergistic enhancement mechanism of the arrayed micropillars. Test results demonstrate that the effective pressure detection range of the sensor spans 0–1038 kPa, accommodating ultra-low pressures such as pulse signals as well as medium-to-high-pressure loads including joint bending. The sensitivity reaches 23.27 kPa⁻¹ within the low-pressure range of 0–200 kPa and remains stable at 3.52 kPa⁻¹ in the high-pressure range of 200–1038 kPa, with piecewise linear fitting correlation coefficients of 0.93 and 0.96 respectively. Both the response time and recovery time of the device are 40 ms, and the hysteresis error throughout the loading-unloading cycle is merely 2.62%. After 20,000 consecutive cyclic loading-unloading tests, the peak capacitance output only decays by 5.1%, verifying outstanding mechanical fatigue resistance and electrical stability. Validations in multi-scenario applications prove that the sensor can accurately capture human physiological and motion signals including radial artery pulses, laryngeal deformation induced by multi-syllable vocalization, and multi-angle bending of fingers and elbow joints, suitable for home-based health monitoring, quantitative rehabilitation training, flexible tactile interaction and other scenarios. The entire fabrication process eliminates high-precision micro-nano processing equipment such as photolithography systems, plasma etchers and 3D printers; only general chemical raw materials and conventional laboratory instruments are adopted. The reusable templates enable low manufacturing costs and large-area coating forming, offering a novel low-cost technical solution for the engineering implementation and industrialization of high-performance iontronic flexible pressure sensors. Full article

In the field of flexible electronics, traditional composite copper foils generally suffer from weak interfacial adhesion between the copper layer and polymer substrate, poor corrosion resistance, insufficient surface uniformity, and limited functional adaptability. To address these issues, Cu/Cu-CeO₂ composite coatings were deposited on polyimide (PI) substrates via PVD magnetron sputtering using argon as the working gas, aiming to enhance the comprehensive properties of composite copper foils, including interfacial bonding strength and corrosion resistance. Initially, pure Cu coatings were deposited on polyimide (PI), polyethylene terephthalate (PET), and polypropylene (PP) substrates. The deposition parameters were optimized through orthogonal and single-factor experiments, and the optimal process combination was determined as follows: PI substrate, sputtering time of 20 min, sputtering power of 60 W, and argon flow rate of 90 sccm, which achieved a balance between mechanical and electrical properties. Subsequently, comparative studies of Ar plasma treatment (100 s, 200 s, 300 s, and 400 s) and NaOH chemical etching (0 mol/L, 1 mol/L, 2 mol/L, and 3 mol/L) were conducted on the three polymer substrates. Comprehensive analyses of water contact angle, surface energy, bonding strength, and surface roughness demonstrated that the PI substrate treated with Ar plasma for 300 s exhibited superior overall performance, with a water contact angle of 48.5°, surface energy of 61.78 × 10⁻³ J/m², bonding strength of 4.56 N, and surface roughness of 0.89 μm. On this basis, the performance of pure Cu coatings and Cu/Cu-CeO₂ composite coatings prepared under different CeO₂ sputtering powers (20 W, 30 W, 40 W, and 50 W) was further investigated. Combined analyses of SEM, EDS, and XPS characterizations, together with bonding strength, resistivity, electrochemical impedance spectroscopy, polarization curves, and corrosion morphology tests, revealed that the Cu/Cu-CeO₂ composite coating prepared at a sputtering power of 50 W exhibited superior overall performance in terms of interfacial bonding strength and corrosion resistance. Full article

We report on results referring to the growth and characterization of Sn-oxide-semiconductor thin films (SnO₂, SnO and intermediate Sn₃O₄) on silicon substrates forming Type II heterojunction band alignment. The samples were produced by a two-step procedure: (a) growth of a metallic Sn layer by RF magnetron sputtering deposition followed by (b) post-growth treatment of the Sn films with oxygen plasma etching for the formation of the oxides in various time steps. Various annealing steps were considered. The structural and chemical properties of the prepared thin films were determined by means of X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS). The results demonstrated the presence of SnO₂ and SnO in a tetragonal structure and the intermediate Sn₃O₄ in a triclinic structure. The electric properties of thin films were investigated with four-probe I–V characteristics under various conditions. The evaluation of their photo-sensing properties was performed by means of photocurrent J–t curves using a solar simulator. We found that the sample with equal concentrations of SnO₂ and SnO exhibited superior responsivity and detectivity values as well as a responsivity of 12.5 A/W and detectivity of 1.1 × 10¹⁰ Jones for V = 0 under yellow light illumination and an intensity of 2 mW/cm². These excellent values, in combination with the low-cost manufacturing, indicate that the method is promising for future applications. Full article

Monocrystalline silicon, with its high refractive index, high infrared transmittance, and excellent dimensional stability, serves as a key optical component in high-energy laser systems, infrared imaging, and guidance fields. Its processing quality directly affects the performance indicators of related systems. To address the challenges of nanoscale precision shape and property control during processing, methods such as ultra-precision cutting, magnetorheological polishing, laser micromachining, ion beam processing, plasma etching, and chemical–mechanical polishing have been adopted to improve the surface shape accuracy and repair defects of monocrystalline silicon components. This paper reviews the research progress of key technologies, including nanoscale precision surface shape control manufacturing technology, nanoscale precision property control generation methods, and combined processes for its nanoscale shape and property control, providing technical support for achieving nanoscale precision shape and property control manufacturing of monocrystalline silicon components. Full article

This study investigates the processing temperature characteristics and etching behavior of fused silica using an atmospheric pressure microwave plasma jet. The temperature distribution within the processing region was measured in real time via infrared thermography. The effects of microwave input power, argon flow rate, and CF₄ flow rate on the processing temperature were systematically examined using a single-factor approach. Experimental results reveal a strong positive correlation between the plasma temperature and microwave power. The temperature initially rises and then declines with increasing argon flow, peaking at 3 slm, while it increases and eventually stabilizes with higher CF₄ flow. Fixed-point etching demonstrates that the etching rate increases with rising processing temperature. Furthermore, heat accumulation during prolonged dwell time leads to a nonlinear increase in the removal rate. This effect can be effectively mitigated by employing a multi-segment processing strategy, enabling more stable and controllable material removal. The effectiveness of this processing method has also been verified on a fused quartz sub-mirror. Full article

Gate definition is a major challenge in p-GaN gate AlGaN/GaN HEMT structures because of the high selectivity and low plasma damage required during the etching process. In this work, self-terminated etching, developed to limit surface damage and loss of the underlying AlGaN layer, is investigated. A comparison of two over-etch chemistries (Cl₂/O₂/N₂ and BCl₃/SF₆) revealed that the oxygen-based process yields superior results in terms of AlGaN surface morphology, producing a smoother surface and a more conformal p-GaN profile, while the fluorine-based process exhibited more anisotropic behavior, leading to p-GaN residues and surface pitting. To address across-wafer non-uniformity, a temperature gradient strategy using the tunable electrostatic chuck was developed. The optimized process was evaluated through automatic defect control and device robustness under drain bias-stress. A total reduction in defectivity and reliable HEMT devices across the wafer under high drain-source bias were achieved. These results demonstrate the effectiveness of the proposed solution, offering significant improvements in process efficiency and manufacturability. Full article

In logic device development, gate-all-around nanosheet field-effect transistors (GAA NSFETs) are widely regarded as the future mainstream architecture. Due to an innovative stacked-channel design, a novel process module of channel release has been introduced, posing significant challenges to device manufacturing. The channel release quality plays a decisive role in the device’s turn-on voltage and operating speed. Meanwhile, the complex interferences are undoubtedly brought by diverse structures and manufacturing thermal budgets of GAA NSFETs. Here, the non-plasma gas etching, which is not yet widely used in the current industry, is adopted for channel release. The influences of nanosheet width, spacing, and annealing conditions on the etching process are systematically studied. A SiGe/Si etching selectivity as high as 87 is achieved. With increasing channel width, a downward trend in the single-sided damage in the central region of Si nanosheets is shown. At >100% over-etching, the Si single-sided damage in structures with different channel spacing is controlled below 1 nm. The intensified diffusion of Ge elements in the SiGe layer and a gradual slowdown of the SiGe etching rate are caused by increasing the annealing temperature. The root mean square (RMS) value of the channel surface roughness is reduced from 0.087 to 0.069 nm by adding the *H radical pretreatment into the process. These findings provide valuable guidance for developing a channel release etching process with high selectivity, low damage, a stable process window, and low fabrication difficulty. Full article

Reactive Ion Etching (RIE) equipment widely employs showerhead-type structures to ensure plasma and etching uniformity; however, geometric degradation of the showerhead nozzle exit during prolonged operation may alter the internal chamber environment and thereby affect process performance. In this study, the effects of showerhead nozzle exit geometric degradation on process characteristics were evaluated for a 300 mm wafer-scale RIE system using a multiphysics numerical approach. A total of 16 analysis cases were constructed according to nozzle position and nozzle exit diameter, and Computational Fluid Dynamics (CFD), electrostatic analysis, and particle tracing analysis were performed sequentially using COMSOL Multiphysics. The results showed that increasing the showerhead nozzle exit diameter decreased both the pressure and velocity at the nozzle exit, while increasing the electric potential near the nozzle exit. These changes led to different wafer-level distributions of neutral and charged species. Neutral species were mainly affected by drag-based transport under the flow field, whereas charged species were influenced by both the flow field and the electric potential distribution. Cases with below-range neutral-species distributions occurred more frequently than cases with above-range distributions, and below-range charged-species distributions were concentrated in cases with larger diameter combinations. These findings indicate that geometric degradation of the showerhead nozzle exit can influence wafer-level reactive-species distributions through coupled fluidic and electrical pathways and may contribute to process non-uniformity. Full article

The extreme thermal loads encountered in fourth-generation synchrotron radiation sources and X-ray free-electron lasers (XFEL) impose stringent requirements on X-ray optical components. Conventional materials such as beryllium and silicon increasingly exhibit limitations under high-energy conditions, including insufficient thermal conductivity, limited radiation stability, and significant absorption losses, rendering them inadequate for next-generation high-energy X-ray optics. In this context, single-crystal diamond, with its high thermal conductivity, low absorption coefficient, and excellent mechanical strength and radiation resistance, has emerged as a promising candidate for high-energy X-ray refractive optics. This review systematically summarizes recent advances in the fabrication and performance optimization of diamond X-ray refractive lenses for high-energy applications. Starting from the evolving demands of modern synchrotron radiation facilities and XFEL, the fundamental requirements for materials and structural design in high-energy X-ray optics are analyzed. Through comparisons with representative materials, the advantages of diamond in thermal management and transmission performance are highlighted. Major micro- and nanofabrication techniques, including femtosecond laser processing, focused ion beam milling, and plasma etching, are comprehensively reviewed, with emphasis on their respective characteristics in terms of processing efficiency, precision control, and damage introduction. The emerging trend of hybrid fabrication strategies is also discussed. Furthermore, the effects of surface roughness, subsurface damage, and crystal defects on wavefront quality and focusing performance are examined, along with corresponding post-processing and surface correction methods. Finally, current challenges related to large-size single-crystal growth, high-precision low-damage fabrication, and long-term operational stability are discussed, and future development directions for diamond-based X-ray refractive optical components are outlined. Full article

Silicon micromachining serves as the foundational enabling technology for high-precision MEMS inertial sensors. However, the relentless pursuit of enhanced sensitivity and multi-functionality in emerging applications encounters a fundamental bottleneck when confined to two-dimensional scaling. The evolution toward complex three-dimensional (3D) stacking architectures is an inevitable trajectory for devices including MEMS inertial sensors, yet performance is constrained by the limitations of conventional processes in fabricating and integrating intricate 3D hollow structures. Specifically, uniformity in large-area deep silicon etching, structural integrity of convex corners in wet etching, and residual stress induced by multi-layer wafer bonding have emerged as critical, shared challenges. To address these issues, this paper proposes a triple-layer wafer-level stacking scheme that synergistically combines wet/dry hybrid etching with low-temperature adhesive bonding. This stacking scheme incorporates an innovative linear compensation model for wet-etched convex corners, enabling high-precision fabrication of complex corner structures under deep etching conditions. Furthermore, a collaborative strategy involving temporary bonding and plasma flow-field optimization improves the uniformity and integrity of dry etching for large perforated structures. A low-temperature triple-layer wafer-level stacking process is developed, encompassing precise adhesive dispensing, optical alignment, and a stepped low-temperature curing profile, thereby achieving highly symmetric 3D integration with controlled adhesive distribution. The efficacy of this stacking scheme is validated through the fabrication of a symmetrically stacked triple-layer MOEMS accelerometer sensing element. Test results demonstrate a noise floor as low as 0.40 µg/√Hz and a bias instability of 1.81 µg over 10 min. Compared with a double-layer counterpart, improved performance is obtained. The wafer-level stacking scheme established in this work not only provides a viable pathway for pushing the manufacturing limits of high-precision inertial devices but also offers a generic methodology for tackling complex hollow structure formation and low-temperature integration, holding referential value for broader applications in high-precision 3D microsystems. Full article

The effects of RF plasma treatments using different gases (Ar, O₂, and N₂) and processing parameters on the surface wettability of polyethylene terephthalate (PET) films were systematically investigated. Atomic force microscopy (AFM) and X–ray photoelectron spectroscopy (XPS) were employed to characterize the evolution of surface topography and chemical composition. While all treatments enhanced hydrophilicity, the magnitude of improvement and the governing mechanisms were gas-dependent. Among them, O₂ plasma treatment exhibited the most pronounced effect: under optimal conditions (20 W, 80 s), the water contact angle (WCA) was reduced to 3.7°, indicating a superhydrophilic surface. This enhancement was primarily attributed to a substantial increase in surface oxygen content (O/C ratio) and the incorporation of strongly polar oxygen-containing functional groups, such as C=O and COOH. N₂ plasma offered moderate improvement via nitrogen-containing groups, while non-reactive Ar plasma relied primarily on physical etching, yielding the smallest enhancement. Analysis revealed that wettability evolution was dominated by increased polar surface energy from chemical functionalization, with surface roughness playing a synergistic role. These results demonstrate that optimizing plasma gas and parameters effectively controls PET wettability through the coupled regulation of surface chemistry and topography. Full article

In the semiconductor industry, fluorinated gases with high global warming potential (GWP) are recognized as significant sources of greenhouse gas emissions. This study presents a measurement-based analysis of a 300 mm wafer etching process using CF4, C4F6, and C4F8 gases. The use rate of gas (Ui), unreacted fraction (1-Ui), and by-product generation rate (Bi) were evaluated under varying plasma intensity conditions. The results show that the unreacted fraction (1-Ui) decreased with increasing plasma intensity for all process gases, indicating enhanced gas dissociation efficiency. In contrast, the by-product generation rate (Bi) exhibited non-linear behavior due to the complex interplay of dissociation and recombination reactions within the plasma. Furthermore, the measured Ui and Bi values showed significant deviations from the default emission factors provided in the 2006 IPCC Guidelines and the 2019 Refinement. Variability analysis based on the coefficient of variation (CV) was conducted using measurements obtained under different plasma conditions (n = 3). The results indicate that Ui exhibited relatively stable behavior with low variability (CV < 0.3), whereas Bi showed higher variability depending on the type of by-product gas, reflecting stronger sensitivity to process conditions. These findings highlight that IPCC default emission factors may not adequately reflect actual process conditions and underscore the importance of incorporating measurement-based, condition-dependent variability into emission estimation. Full article

Freestanding graphene exhibits exceptional mechanical flexibility and electrical conductivity, making it well suited for varying capacitance applications. For example, when suspended above a fixed electrode, graphene will move in response to an applied bias voltage, thereby forming a varactor or voltage-controlled capacitor. In this work, we present a very detailed and scalable fabrication process for building graphene-based variable capacitor device structures. Starting with commercially available 100 mm silicon wafers with a thick thermal oxide layer, we fabricate thousands of individually accessible freestanding graphene variable capacitors using standard semiconductor methods. The process begins with metal deposition to establish alignment crosshairs, then oxide etching to create trenches, a second metal deposition to form electrodes and bonding pads, followed by large-area graphene transfer, then patterning the graphene via oxygen plasma etching, critical point drying for suspension, and finally wire bonding our devices into a package. We use optical and atomic force microscopy characterization to confirm our design specifications were met. Electrical characterization confirms successful graphene suspension through voltage-dependent capacitance measurements. The procedure presented here successfully suspends both pure multilayer graphene as well as graphene with a thick layer of PMMA. Full article

Fueled by the push for “More than Moore”, three-dimensional integrated circuits (3D ICs) have become a backbone of next-generation electronics. Their complex architectures place unprecedented demands on etching technologies, which must now deliver atomic precision, stringent high-aspect-ratio (HAR) control, and virtually damage-free profiles. Meeting these challenges requires metrology capable of true 3D, quantitative analysis at the nanoscale. Atomic force microscopy (AFM) has proven essential in this regard, offering non-destructive, sub-nanometer characterization that other techniques cannot provide. This review systematically examines AFM’s pivotal role in advancing key etching processes for 3D ICs, including deep reactive ion etching of through-silicon vias (TSVs), atomic layer etching (ALE), and cryogenic plasma etching. We detail AFM’s unique contributions to quantifying sidewall roughness, verifying etch-per-cycle rates, and assessing surface damage. We also discuss how recent innovations, such as tilting-AFM, HAR probes, and automated inline systems, are overcoming traditional barriers in throughput and access to sidewalls and deep trenches. Looking forward, the integration of AFM with optical metrology, machine learning, and multi-scale modeling opens a path toward truly autonomous process control and optimization. As such, AFM stands as an indispensable tool for developing and refining the etching processes that underpin next-generation 3D semiconductor manufacturing. Full article