Vertical Stacking Research Articles

Synthesis of NbSe2/Bilayer Nb‐Doped WSe2 Heterostructure from Exfoliated WSe2 Flakes

Forming heterostructures of 2D metals and semiconductors using chemical vapor deposition (CVD) has significant potential to effectively reduce contact resistance in electronic devices. However, semiconducting transition metal dichalcogenide (TMD) layers in metal–semiconductor heterostructures are currently restricted to monolayers despite the superior mobility and density of states in bilayer TMDs. Herein, NbSe2/bilayer Nb‐doped WSe2 metal/semiconductor heterostructure from exfoliated WSe2 flakes are synthesized first. The exfoliated WSe2 bulk crystals on an Nb‐coated substrate are heated to 950 °C under a flow of selenium vapor, and then the NbSe2/bilayer Nb‐doped WSe2 heterostructures are formed. Statistics on the number of Nb‐doped WSe2 layers grown on a 1 cm × 1 cm CVD substrate shows that 65% of the Nb‐doped WSe2 layers are grown as bilayers. X‐ray photoelectron spectroscopy, optical microscopy, and transmission electron microscopy clearly clarify the number of Nb‐doped WSe2 layers and heterostructure of NbSe2/bilayer Nb‐doped WSe2. Electrical measurements using Cr contacts show that bilayer Nb‐doped WSe2 displays 7‐ and 10‐times higher mobility and on/off ratio than monolayer Nb‐doped WSe2. The mobility and on/off ratio are further doubled in NbSe2/bilayer Nb‐doped WSe2 contact compared to Cr/bilayer Nb‐doped WSe2 contact, attributed to a clean interface in vertical stack heterostructure, enhancing electrical performance.

Theoretical Perspective of Enhancing Order in n-Doped Thermoelectric Polymers through Side Chain Engineering: The Interplay of Counterion-Backbone Interaction and Side Chain Steric Hindrance.

Donor-acceptor (D-A) copolymers doped with n-type dopants are widely sought after for their potential in organic thermoelectric devices. However, the existing structural disorder significantly hampers their charge transport and thermoelectric performance. In this Letter, we propose a mechanism to mitigate this disorder through side chain engineering. Utilizing molecular dynamics simulations, we demonstrate that strong Coulomb interactions between counterions and charged polymer backbones induce a transition in the stacking arrangement of the polymer backbones from a slipped to a vertical configuration. However, the presence of side chain steric hindrance impedes the formation of closely packed and ordered vertical stacking arrangements, resulting in greater distances between adjacent backbones and a higher level of structural disorder in the doped films. Therefore, we propose minimizing side chain steric hindrance to enhance the structural order in doped films. Our findings provide essential insights for advancing high-performance thermoelectric polymers.

Quantum Conductance in Vertical Hexagonal Boron Nitride Memristors with Graphene-Edge Contacts.

Two-dimensional materials (2DMs) have gained significant interest for resistive-switching memory toward neuromorphic and in-memory computing (IMC). To achieve atomic-level miniaturization, we introduce vertical hexagonal boron nitride (h-BN) memristors with graphene edge contacts. In addition to enabling three-dimensional (3D) integration (i.e., vertical stacking) for ultimate scalability, the proposed structure delivers ultralow power by isolating single conductive nanofilaments (CNFs) in ultrasmall active areas with negligible leakage thanks to atomically thin (∼0.3 nm) graphene edge contacts. Moreover, it facilitates studying fundamental resistive-switching behavior of single CNFs in CVD-grown 2DMs that was previously unattainable with planar devices. This way, we studied their programming characteristics and observed a consistent single quantum step in conductance attributed to unique atomically constrained nanofilament behavior in CVD-grown 2DMs. This resistive-switching property was previously suggested for h-BN memristors and linked to potential improvements in stability (robustness of CNFs), and now we show experimental evidence including superior retention of quantized conductance.

Flexible switch matrix addressable electrode arrays with organic electrochemical transistor and pn diode technology

Due to their effective ionic-to-electronic signal conversion and mechanical flexibility, organic neural implants hold considerable promise for biocompatible neural interfaces. Current approaches are, however, primarily limited to passive electrodes due to a lack of circuit components to realize complex active circuits at the front-end. Here, we introduce a p-n organic electrochemical diode using complementary p- and n-type conducting polymer films embedded in a 15-μm -diameter vertical stack. Leveraging the efficient motion of encapsulated cations inside this polymer stack and the opposite doping mechanisms of the constituent polymers, we demonstrate high current rectification ratios (105\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{5}$$\\end{document}) and fast switching speeds (230 μs). We integrate p-n organic electrochemical diodes with organic electrochemical transistors in the front-end pixel of a recording array. This configuration facilitates the access of organic electrochemical transistor output currents within a large network operating in the same electrolyte, while minimizing crosstalk from neighboring elements due to minimized reverse-biased leakage. Furthermore, we use these devices to fabricate time-division-multiplexed amplifier arrays. Lastly, we show that, when fabricated in a shank format, this technology enables the multiplexing of amplified local field potentials directly in the active recording pixel (26-μm diameter) in a minimally invasive form factor with shank cross-sectional dimensions of only 50×8 μm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu m}^{2}$$\\end{document}.

Interfacial Charge Transfer for Enhancing Nonlinear Saturable Absorption in WS2/graphene Heterostructure.

Interlayer charge-transfer (CT) in 2D atomically thin vertical stacks heterostructures offers an unparalleled new approach to regulation of device performance in optoelectronic and photonics applications. Despite the fact that the saturable absorption (SA) in 2D heterostructures involves highly efficient optical modulation in the space and time domain, the lack of explicit SA regulation mechanism at the nanoscale prevents this feature from realizing nanophotonic modulation. Here, the enhancement of SA response via CT in WS2/graphene vertical heterostructure is proposed and the related mechanism is demonstrated through simulations and experiments. Leveraging this mechanism, CT-induced SA enhancement can be expanded to a wide range of nonlinear optical modulation applications for 2D materials. The results suggest that CT between 2D heterostructures enables efficient nonlinear optical response regulation.

Broadband nonlinear optical response and sub-picosecond carrier dynamics in graphene-SnSe2 van der Waals heterostructures.

The van der Waals (vdWs) heterostructures, with vertical layer stacking structure of various two-dimensional (2D) materials, maintain the reliable photonic characteristics while compensating the shortcomings of the participating individual components. In this work, we combine the less-studied multilayer tin selenide (SnSe2) thin film with one of the traditional 2D materials, graphene, to fabricate the graphene-based vdWs optical switching element (Gr-SnSe2) with superior broadband nonlinear optical response. The transient absorption spectroscopy (TAS) measurement results verify that graphene acts as the recombination channel for the photogenerated carrier in the Gr-SnSe2 sample, and the fast recovery time can be reduced to hundreds of femtoseconds which is beneficial for the optical modulation process. The optical switching properties are characterized by the I-scan measurements, exhibiting a saturable energy intensity of 2.82 mJ·cm-2 (0.425 µJ·cm-2) and a modulation depth of 15.6% (22.5%) at the wavelength of 1030 nm (1980nm). Through integrating Gr-SnSe2 with a cladding waveguide, high-performance picosecond Q-switched operation in the near-infrared (NIR) and mid-infrared (MIR) spectral regions are both achieved. This work experimentally demonstrates the great potential of graphene-based vdWs heterostructures for applications in broadband ultrafast photonics.

Review on Multilayer Farming: A Way Towards Farmer Prosperity

Multilayer farming is an innovative agricultural strategy that redefines traditional farming practices by harnessing vertical space to cultivate multiple layers of crops within a single agricultural system. This approach is designed to overcome challenges associated with land scarcity and inefficient land use. The concept involves arranging different crops in layers, utilizing the vertical dimension to its fullest extent. The layers can include ground-level crops, vines climbing on trellises, and even trees or shrubs, creating a multi-tiered ecosystem. This arrangement optimizes sunlight exposure, nutrient distribution, and water usage, resulting in enhanced productivity. One of the key advantages of multilayer farming is its potential to significantly increase overall yield per unit of land. By strategically combining plants that complement each other in terms of growth patterns, resource requirements, and ecological interactions, farmers can create a symbiotic environment that maximizes the use of available resources. Resource efficiency is a focal point in multilayer farming. The intercropping of different plant species helps in nutrient cycling, reducing the need for external inputs. Furthermore, the diverse plant composition can deter pests and diseases, reducing the reliance on chemical interventions. The vertical stacking of crops also allows for efficient water usage through integrated irrigation systems. Beyond its practical benefits, multilayer farming contributes to biodiversity preservation. The coexistence of various plant species fosters a more resilient and ecologically diverse agricultural landscape. This can have positive effects on soil health, pollination, and overall ecosystem stability.

New structure transistors for advanced technology node CMOS ICs.

Over recent decades, advancements in complementary metal-oxide-semiconductor integrated circuits (ICs) have mainly relied on structural innovations in transistors. From planar transistors to the fin field-effect transistor (FinFET) and gate-all-around FET (GAAFET), more gate electrodes have been added to three-dimensional (3D) channels with enhanced control and carrier conductance to provide higher electrostatic integrity and higher operating currents within the same device footprint. Beyond the 1-nm node, Moore's law scaling is no longer expected to be applicable to geometrical shrinkage. Vertical transistor stacking, e.g.in complementary FETs (CFET), 3D stack (3DS) FETs and vertical-channel transistors (VFET), for enhanced density and variable circuit or system design represents a revolutionary scaling approach for sustained IC development. Herein, innovative works on specific structures, key process breakthroughs, shrinking cell sizes and design methodologies for transistor structure research and development are reviewed. Perspectives on future innovations in advanced transistors with new channel materials and operating theories are also discussed.

Impact of Graphitization Degree on the Electrochemical and Thermal Properties of Coal.

Coal-based cryptocrystalline graphite is an intermediate phase formed during the transformation of highly metamorphic anthracite into crystalline graphite. In order to explore the relationship between the graphitization degree of coal-based cryptocrystalline graphite and its physical properties from macromolecular structure to provide a theoretical basis for industrial application, samples were tested by X-ray diffraction, electrochemistry, and thermal conductivity and compared with standard graphite (SG) and artificial thermal simulation graphitized samples. The results show that with the increase of graphitization degree and the growth of microcrystalline structure, the electrical impedance of cryptocrystalline graphite decreases, the conductivity increases, the specific capacity of initial discharge increases, and the thermal conductivity increases, which gradually approach the electrical and thermal properties of crystalline graphite. The linear equations between impedance and La and Lc are y = -0.42x + 70.44 and y = -1.87x + 70.62, and the correlation coefficients are 0.93 and 0.88. The linear equations between thermal conductivity and the horizontal extension length (La) and vertical stacking thickness (Lc) are y = 0.09x + 1.36 and y = 0.4x + 0.76, the correlation coefficients are 0.82 and 0.84., and the reduction of microcrystalline parameters d002 and the increase of La and Lc lead to a direct improvement of physical properties. Artificial thermal simulation samples also show the same regularity, but their physical properties are lower than those of natural evolution samples. Short-term high-temperature simulation is different from long-term magma heat and pressure, and the growth of graphite microcrystals is more complete under long-term geological conditions, resulting in better physical properties.

Influence of structural defect and sample size on thermal conductivity of gallium selenide/graphene

The thermal conductivity (TC) of graphene-based vertical stacking material has recently attracted a lot of researchers based on its ability to help the thermal management of nanoelectronics devices due to the multifunctional properties of these engineered materials. Herein, we analyze the thermal conductivity of pristine/nanoporous gallium selenide/graphene heterostructure (GaSeGrHs) and gallium selenide (GaSe) using non-equilibrium molecular dynamics (NEMD) simulations. The influence of temperature difference/averaged temperature/sample length/pore shape on GaSeGrHs and GaSe was investigated. Due to the high graphene substrate's TC, the TC of the GaSeGrHs sheet is much bigger than the GaSe sheet. The results calculated by NEMD are similar to those calculated from the theoretical prediction formula and unaffected by temperature differences between the two thermal sources of hot and cold. Besides, the thermal conductivities of nanoporous GaSeGrHs are notably smaller than those of pristine ones. Also, the pore shapes can finely tune the TCs as well as the distribution of temperature around the membrane pore. Besides, the TC of pristine GaSeGrHs increases as the sample size rises from 10 to 70 nm and the temperature drops from 800 K to 100 K. In fact, with increasing average temperature, the GaSeGrHs TC drops 64 % and 54.7 % in ZZ and AC directions compared to the GaSe TC with 88.66 % and 89.66 %, respectively. Overall, the study would better understand the thermal conductivity of GaSeGrHs under various investigated conditions. It would extend its successful applications of these 2D materials in nanoelectronic, spintronic, and thermoelectric devices.

Parasitic Capacitance Model for Stacked Gate-All-Around Nanosheet FETs

Gate-all-around (GAA) nanosheet field-effect transistors (NSFETs) are hailed as the most promising architecture for the incessant scaling of MOSFETs to the sub-5-nm technology node and beyond. Although the GAA structure and the ultra-thin channel lead to a significantly improved static performance owing to the enhanced electrostatic integrity and higher immunity against the short-channel effects, the vertical stacking and the inherent 3-D-geometry result in a large parasitic capacitance and may degrade the dynamic performance. Therefore, it becomes imperative to analyze the parasitic capacitance components in GAA NSFETs and provide design guidelines for optimizing the dynamic performance. To this end, in this work, we have formulated an analytical model for the total gate parasitic capacitance in GAA NSFETs, considering contributions from different parasitic capacitance components. Furthermore, we have also investigated the variation in parasitic capacitance components with the structural parameters for design optimization of GAA NSFETs from a dynamic performance perspective. The result of the developed model is in good agreement with TCAD simulation result indicating the efficacy of the analytical model.

Tunable, multifunctional opto-electrical response in multilayer FePS3/single-layer MoS2 van der Waals p-n heterojunctions.

The combination of specific van der Waals semiconductors in vertical stacks leads to atomically sharp heterointerfaces with unique properties, offering versatility and additional functionality for thin, flexible, optoelectronic devices. In this work, we demonstrate heterostructures built from single-layer MoS2 (n-type) and multilayer FePS3 (p-type) as multifunctional p-n junctions where robust photoluminescent light emission and broadband electrical photo-response coexist. This is made possible by the inherent properties of the materials involved and the precise energy band alignment at their interface, which preserves the photoluminescent emission provided by the single-layer MoS2 and confers exceptional tunability to the system. Indeed, through small changes in the applied voltage across the junction, the interplay between photoluminescence and photocurrent generation can be tuned, allowing for a precise control of the light emission of single-layer MoS2 - from severely quenched to an order of magnitude enhancement. Additionally, the broadband photo-response of the system presents an enhanced performance under ultraviolet illumination, in contrast to other van der Waals heterostacks containing single-layer semiconductors. Furthermore, this photo-response can be adjusted by the application of an external electric field, enabling photocurrent generation under both reverse and forward bias, thereby contributing to the overall functionality and versatility of the system.

Shelf and Lower-Shoreface Deposits in the Upper Midway Group and the Transition into Fluvial-Dominated Deltaic Deposits in the Hooper Formation (Lower Wilcox Group) in the Southeastern Texas Gulf Coast

The Paleocene Upper Midway Group in the southeastern Texas Gulf Coast records a stratigraphic succession of shelf and lower-shoreface systems. Four (4) recognition criteria for these systems include (1) thin (<2 ft [<0.6 m]), erosion-based and lenticular, very fine-grained and fine-grained sandstone beds with swaley cross-stratification, (2) a diverse Cruziana trace-fossil assemblage consisting of Teichichnus, Palaeophycus, Planolites, and Schaubcylindrichnus, (3) net-sandstone trends consisting of strike-elongate ribbons and pods that merge updip (north and northwest) into broad, sheet-like patterns, and (4) an absence of northwestern and northern feeder systems inferred from net-sandstone maps. Net-sandstone trends in Upper Midway shelf deposits in southeastern Texas are irregular and narrow, strike-elongate pods and ribbons ranging in thickness from 20 to 35 ft (6 to 11 m). They grade southward and southeastward into extensive, muddy areas with <10 ft (<3 m) of net sandstone. In contrast, lower-shoreface deposits at the top of the Upper Midway Group contain wide (>10 mi [>16 km]) strike-elongate belts of >40 ft (>12 m) of net sandstone. These belts extend northeastward >50 mi (>80 km) along depositional strike. Sandstone-body continuity, inferred from wireline-log cross-sections, differs greatly among these shelf and lower-shoreface deposits. Sandstone-body continuity in Upper Midway lower-shoreface deposits at 10 mi (16 km) well spacing is approximately 60%, whereas it is only 20% at the same well spacing in shelf deposits. At 20 mi (32 km) well spacing, lower-shoreface sandstone-body continuity is 37% but only 4% in shelf deposits. Microscale heterogeneity in the Upper Midway Group is related to sedimentary structures and accessory features that disrupt vertical sandstone-bed continuity over scales of millimeters to centimeters. These include mudstone drapes, scour surfaces, shell debris, mudstone clasts, and trace fossils. Mesoscale heterogeneity, inferred from cores and wireline-log cross-sections, is defined by lateral sandstone-body pinchouts and vertical stacking patterns. In contrast, macroscale heterogeneities in the Upper Midway Group, inferred from net-sandstone maps, compose facies architecture at a regionally-mappable scale. They include paleogeographic elements such as shelf sand-shoal complexes, strike-fed shoreface systems, and abandoned-deltaic headlands. These paleogeographic elements extend for tens of miles or kilometers along depositional strike from southwest to northeast. The transition in depositional systems in the Upper Midway Group to the Lower Wilcox Group is abrupt, recording a change from wave-dominated shelf and shoreface systems to fluvial-dominated deltaic depositional systems. Dip-elongate, fluvial-dominated deltaic deposits at the base of the Wilcox Group (Hooper 1 depositional unit) have depositional axes oriented orthogonally with respect to those in the underlying Midway Group. Hooper 1 depositional axes are narrow (commonly <4 mi [<6.4 km] across. They are erosionally-based, net upward-fining, and composed of fine- to medium-grained sandstone with abundant siltstone and mudstone rip-up clasts. Distributary-channel trends in the Hooper 1 depositional unit are connected southward and southwestward to downdip-bifurcating trends representing upward-coarsening sub-delta deposits that pinch out into interdistributary mudstones. Microscale heterogeneity in fluvial-dominated deltaic deposits in the lower part of the Hooper Formation occurs at the scale of large (>2 in [>5.1 cm]) diameter siltstone and mudstone clasts in distributary-channel deposits. Mesoscale heterogeneity is controlled by lateral pinchouts of distributary-channel sandstone bodies into floodplain and interdistributary mudstones. Macroscale heterogeneity is represented by numerous dip-elongate distributary-channel depositional axes that segment lower-coastal-plain systems into discrete sandy depocenters. Six Hooper 1 deltaic depocenters occur along a 60 mi (96 km) span along the Angelina-Caldwell Flexure. Sandstone-body continuity along depositional strike (southwest to northeast) in the Hooper 1 depositional unit is poor, being only approximately 25% at 10 mi (16 km) well spacing. These sandstone-body continuity values record the presence of multiple, locally occurring deltaic depocenters within a fluvial-dominated deltaic system, in contrast to the wave-dominated shelf and lower-shoreface deposits in the underlying Upper Midway Group.

The Influence of Reservoir Architecture on the Connectivity of the Shahejie Formation in the Liuzhong Oilfield

The lack of research on fine reservoir structure and sand body patterns in the Jidong Oilfield currently restricts the efficient development of the oilfield. Therefore, this article mainly focuses on the study of the main types of facies of the Shahejie Formation, sand body splicing patterns, and the degree of sand-body connectivity. The interpretation and analysis of well-logging, three-dimensional (3D) seismic, and production data were used to lay the foundation for the study and evaluate the remaining oil distribution. The results indicate that the reservoir sandstones in the study area were mainly deposited in a submerged distributary channel, mouth bar, and distributary channel flank. Using logging information to identify individual sands, a deltaic sand assemblage pattern is proposed by analyzing the sedimentary architecture. In the vertical direction, the deltaic sand body collocation style can be divided into cut-and-stack and separated types. In the lateral direction, the multi-stage sand bodies exhibit three collocation patterns: the side-cutting type, the mouth bar contact type, and the submerged distributary channel flank contact type. The degree of sand-body connectivity under different splicing patterns was analyzed and verified using production dynamic data. It was found that the sand body splicing pattern with a vertical up-cut stack and the sand body splicing pattern with a lateral up-cut had the best inter-sand-body connectivity.

Design and Analysis Challenges of 3D Multi-Chiplet Heterogenous Architectures

As demands accelerate for increasing density, higher bandwidths, and lower power, many IC design and packaging teams are taking a close look at vertical stacking multiple chips and chiplets. This technology, called 3D-IC, promises many advantages over traditional single-die planar designs. Some are using the term ‘More-than-Moore’ to describe the potential of this new technology. Integration by stacking die and using advanced packaging technologies allows designers to cram more functionality into much smaller form factors, while improving performance and reducing costs. Whether you are an ASIC designer or package designer, you can expect several new design and analysis challenges when transitioning from the world of single die architectures to the world of More-than-Moore. This presentation will describe many of these new challenges facing design teams as they transition to the world of multi-chiplet 3D architectures, both on the die side and the packaging side of design. Additionally, novel solutions to many of these challenges will be presented.

An experimental study on horizontal well waterflooding in the Cretaceous porous carbonate reservoir of Oman

Porous carbonate reservoirs, prevalent in the Middle East, are lithologically dominated by bioclastic limestones, exhibiting high porosity, low permeability, intricate pore structure, and strong heterogeneity. Waterflooding through horizontal wells is commonly used for exploiting these reservoirs. However, challenges persist, such as significant uncertainty and complex operational procedures regarding adjustment effects during the exploitation. The USH reservoir of the Cretaceous D oilfield, Oman exemplifies typical porous carbonate reservoirs. It initially underwent depletion drive using vertical wells, followed by horizontal well waterflooding in the late stage. Currently, the oilfield is confronted with substantial developmental challenges, involving the understanding of residual oil distribution, effective water cut control, and sustaining oil production since it has entered the late development stage. Employing a microscopic visualization displacement system equipped with electrodes, this study elucidated the waterflooding mechanisms and residual oil distribution in the late-stage development of the USH reservoir. The results reveal that the reservoir's vertical stacking patterns act as the main factor affecting the horizontal well waterflooding efficacy. Distinct water flow channels emerge under varying reservoir stacking patterns, with post-waterflooding residual oil predominantly distributed at the reservoir's top and bottom. The oil recovery can be enhanced by adjusting the waterflooding's flow line and intensity. The findings of this study will provide theoretical insights of waterflooding mechanisms and injection-production adjustments for exploiting other porous carbonate reservoirs in the Middle East through horizontal wells.

Space-Confined Synthesis of Monolayer Graphdiyne in MXene Interlayer.

Graphdiyne (GDY) is an artificial carbon allotrope that is conceptually similar to graphene but composed of sp- and sp2 -hybridized carbon atoms. Monolayer GDY (ML-GDY) is predicted to be an ideal 2D semiconductor material with a wide range of applications. However, its synthesis has posed a significant challenge, leading to difficulties in experimentally validating theoretical properties. Here, it is reported that in situ acetylenic homocoupling of hexaethynylbenzene within the sub-nanometer interlayer space of MXene can effectively prevent out-of-plane growth or vertical stacking of the material, resulting in ML-GDY with in-plane periodicity. The subsequent exfoliation process successfully yields free-standing GDY monolayers with micrometer-scale lateral dimensions. The fabrication of field-effect transistor on free-standing ML-GDY makes the first measurement of its electronic properties possible. The measured electrical conductivity (5.1 × 103 S m-1 ) and carrier mobility (231.4 cm2 V-1 s-1 ) at room temperature are remarkably higher than those of the previously reported multilayer GDY materials. The space-confined synthesis using layered crystals as templates provides a new strategy for preparing 2D materials with precisely controlled layer numbers and long-range structural order.

Low-temperature Cu/SiO2 hybrid bonding based on Ar/H2 plasma and citric acid cooperative activation for multi-functional chip integration

Cu/SiO2 hybrid bonding is a crucial technique for three-dimensional (3D) integration, which can greatly shorten the interconnected spacing by metal-electrode (Cu) and insulator (SiO2) hybrid interfaces without requiring microbumps. By this bumpless hybrid bonding, the vertical stack of devices with ultrahigh density can be accomplished to meet the demand of high-performance artificial intelligence (AI) chips. To improve the compatibility for multi-functional chip integration, low-temperature bonding conditions are essential. Moreover, it is a great challenge to achieve oxide-free Cu/Cu bonding interface as well as ensure SiO2/SiO2 bonding with sufficient hydroxylated groups. Therefore, we proposed a two-step cooperative activation process as argon and hydrogen gas mixture (Ar/H2) plasma activation followed by citric acid treatment, which makes the Cu oxide reduction and SiO2 hydroxylation simultaneously. The low-cost Cu/SiO2 hybrid bonding was successfully obtained at 200 °C in ambient air. There were nearly neither oxides at Cu/Cu bonding nor residual carbon at SiO2/SiO2 bonding interfaces. More interestingly, the bonding pairs not only survived in the aging tests in the range of 150–350 °C, but the bonding area and strength were further improved. Consequently, this two-step cooperative activation process has great potential for low-temperature Cu/SiO2 hybrid bonding with high-temperature reliability.

Using M-Series with Adaptive Patterning to shrink PCB systems into System-In-Packages

Traditional system-level design typically includes several Integrated Circuits (IC’s) that get individually packaged and implemented onto a Printed Circuit Board (PCB). This PCB includes the required support circuitry for the IC’s to complete the full system design. This architecture creates a system that is far larger and more power intensive than a single package. It also suffers from greater bandwidth and signal integrity limitations. To counter these shortcomings, many companies are migrating away from PCB to System-in-Package (SiP) designs. In a SiP design, these chips are integrated into a single package along with all the supporting passive devices. The die of the package may be configured through vertical stacking or lateral interconnects to improve design density. For semiconductor companies that design both the IC’s and the system-level PCB, there is an emerging trend in which the existing PCB designs are reused and re-purposed to generate a new SiP design. This allows for companies to leverage known-good design data to create a smaller form factor, higher density package, while requiring fewer engineering design hours. While the prominent solution for SiP designs has been laminate substrates, as the demand for further density scaling and heterogeneous integration grows, advanced packaging technologies are being leveraged. Using a fan-out RDL based solution can accommodate increased interconnect density and reduced layer count as compared to a laminate substrate. Deca’s Adaptive Patterning® technology ensures companies are able to manufacture fan-out wafer-level packages (FOWLP) with the highest possible yield. This paper details the benefits of migrating from PCB to package level integration as well as how utilizing Adaptive Patterning® technology further benefits this migration with increased density and performance as compared to traditional packaging technology

Stacked ring resonators for optical vortices

In this paper, we study transmission of higher-order modes, optical vortices (OVs) included, through a bus fiber coupled to a vertical stack of ring resonators—stack multi-ring resonator (SMR). We show that transmission curves for OVs feature a characteristic gap-like structure, whose presence we explain as a manifestation of the band structure of an infinite stack of coupled ring resonators. We show a principal possibility to use SMRs as elements of delay lines for fiber optics communications on orbital angular momentum (OAM) states. We emphasize the advantages of such systems as delay lines for communications that use as signal carriers odd and even Laguerre–Gaussian (LG) modes. We also show that SMRs are able to exert super-efficient parametric control over the OAM of the transmitted optical field, as well as to generate OAM beams from odd and even LG modes.