Silicon Substrate Research Articles

Back side power delivery: Revolutionizing chip design

Backside power delivery network technology represents a revolutionary advancement in semiconductor design, addressing critical power distribution challenges in advanced process nodes. This architectural innovation separates power delivery from signal routing through vertical integration, enabling significant improvements in chip performance and efficiency. The approach incorporates nano-Through Silicon Vias for direct power delivery through thinned silicon substrates, dramatically reducing routing congestion and IR drop while enhancing signal integrity. Intel's PowerVia implementation, alongside developments from other major semiconductor manufacturers, demonstrates the technology's potential to transform power delivery architectures. The solution not only improves thermal management and reduces voltage droop but also enables greater design flexibility through simplified routing and optimized circuit implementation. Despite initial manufacturing complexities, the long-term benefits include enhanced yield rates, reduced design cycles, and improved performance metrics. The technology's adoption across the semiconductor industry marks a pivotal shift in power delivery architecture, positioning it as a crucial enabler for future semiconductor scaling and high-performance computing applications.

Effect of UV Light Exposure Duration on the Removal of Exfoliation Agent Residues in Two-Dimensional Perovskite Nanosheets: An AFM Study.

Accurate determination of dielectric properties and surface characteristics of two-dimensional (2D) perovskite nanosheets, produced by chemical exfoliation of layered perovskites, is often hindered by exfoliation agent residues such as tetrabutylammonium (TBA). This study investigates the effect of ultraviolet (UV) light exposure duration on the removal of TBA residues from 2D Ca2NaNb4O13- nanosheets deposited on silicon substrates via Langmuir-Blodgett method using atomic force microscopy (AFM). Nanoscale adhesion forces between silicon AFM tips and nanofilms exposed to UV light for 3, 12, 18, and 24 hours were measured. Nanofilms exposed to UV for 12 hours showed significant heterogeneity in adhesion forces compared to control nanofilms not exposed to UV. This heterogeneity improved after 18 hours and reached maximum homogeneity at 24 hours. A noticeable decrease in adhesion forces indicated a reduction in TBA residues after 18 hours, with further reduction observed at 24 hours. The most probable adhesion forces for control nanofilms and those exposed to UV for 3 and 12 hours were 1.6-fold and 2.0-fold higher, respectively, compared to nanofilms exposed to UV for 18 and 24 hours. Similarly, surface roughness peaked at 12 hours and then decreased with longer exposure, resulting in a smoother surface at 24 hours.

Single-step, conformal, and efficient assembly of ligand-exchanged quantum dots for optoelectronic devices via an electric field.

Quantum dots (QDs) are promising materials for optoelectronic applications, but their widespread adoption requires controllable, selective, and scalable deposition methods. While traditional methods like spin coating and drop casting are suitable for small-scale deposition onto flat substrates, and ink-jet printing offers precision for small areas, these methods struggle with conformal deposition onto non-planar, large area substrates or selective deposition onto large area chips. Electrophoretic deposition (EPD) is an efficient and versatile technique capable of achieving conformal and selective area deposition over large areas, but its application to QD films has been limited. Previous EPD studies on QD films used QDs with native ligands, which hinder charge transport in optoelectronic devices. Here, we combined in-solution ligand exchange with EPD to deposit dense PbSe QD films. Through solvent engineering, we controlled the growth rate of PbSe QD films and used an in situ quartz crystal microbalance to measure the growth rate as a function of applied potential. We demonstrated the efficacy of this methodology by conformally depositing PbSe QD films onto textured silicon substrates via EPD and fabricating infrared photodetectors. The responsivity of the as-fabricated IR PDs at 1200 nm was ∼0.01 A W-1 and response times were 4.6 ms (on) and 4.7 ms (off).

ScAlN/GaN High Electron Mobility Transistor Heterostructures Grown by Ammonia Source Molecular Beam Epitaxy on Silicon Substrate

In this work, ammonia source molecular beam epitaxy is explored as an alternative technique to grow ScAlN/GaN high electron mobility transistor heterostructures on a silicon substrate with thin buffer layers. The effect of ScAlN barrier thickness is investigated. A transistor with a maximum drain current superior to 1 A mm−1 has been fabricated on a silicon substrate despite the ohmic contacts having a resistance around 1 ohm.mm, and functional transistors with barriers as thin as 10 nm have been demonstrated.

Epitaxial Growth of Bi2Se3 Thin Films by Thermal Evaporation for the Application of Electrochemical Biosensors

Bi2Se3 is a typical topological material with the gapless surface state, which has many potential applications. In this work, high‐quality Bi2Se3 thin films are prepared by co‐evaporating bismuth and selenium on (100) silicon substrate, followed by in‐situ annealing process. The key parameters are optimized, including growth temperature and the flux ratio of Bi and Se. The crystal orientation and quality of the thin films are characterized by X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, and atomic force microscopy. Furthermore, Bi2Se3 thin films are employed as the working electrode of the biosensor, and their sensitive detection of SARS‐CoV‐2 characteristic gene fragments in the COVID‐19 epidemic is investigated. The cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy demonstrate that the DNA biosensor is successfully constructed based on Bi2Se3 thin films. This study develops a method of the large‐scale homogeneous Bi2Se3 thin films growth by thermal evaporation technology, which has great application potential in electrochemical biosensors.

TiO2/SWCNts: Linear and Nonlinear Optical Studies for Environmental Applications

A series of single-walled carbon nanotube/titanium dioxide (SWCNTs/TiO2) composites were prepared by the incorporation of various concentrations (0, 5, 10, 20 V.%) of SWCNTs in TiO2. The prepared solutions were successfully formed on silicon and quartz substrates using the sol–gel spin-coating approach at 600 °C in ambient air. The X-ray diffraction method was used to investigate the structure of the samples. The absorbance and transmittance data of the samples were measured using a UV–vis spectrophotometer. Through the analysis of these data, both the linear and nonlinear optical properties of the samples were examined. Wemple–DiDomenico’s single-oscillator model was used to calculate the single-oscillator energy and dispersion energy. Finally, all samples’ photocatalytic performance was studied by the photodegradation of methylene blue (MB) in an aqueous solution under UV irradiation. It is found that the photocatalytic efficiency increases when increasing the SWCNT content. This research offers a new perspective for the creation of new photocatalysts for environmental applications.

Direct observations of nucleation and early-stage growth of Au-catalyzed GaAs nanowires on Si(111).

Developing a reliable procedure for the growth of III-V nanowires (NW) on silicon (Si) substrates remains a significant challenge, as current methods rely on trial-and-error approaches with varying interpretations of critical process steps such as sample preparation, Au-Si alloy formation in the growth reactor, and nanowire alignment. Addressing these challenges is essential for enabling high-performance electronic and optoelectronic devices that combine the superior properties of III-V NW semiconductors with the well-established Si-based technology. Combining conventional scalable growth methods, such as Metalorganic Chemical Vapor Deposition (MOCVD) with in situ characterization using Environmental Transmission Electron Microscopy (ETEM-MOCVD) enables a deeper understanding of the growth dynamics, if that knowledge is transferable to the scalable processes. We report on successful epitaxial growth of Au-catalyzed GaAs NWs on Si(111) substrates using micro-electromechanical system (MEMS) chips with monocrystalline Si-cantilevers in both conventional MOCVD and ETEM-MOCVD systems. The conventional MOCVD provided a framework for initial parameter tuning, while ETEM-MOCVD offered valuable insights into early nucleation and catalyst-substrate interactions. Our findings show that nucleation is significantly influenced by the removal of native oxide layers and the initial formation of the Au-Si alloy. Our in situ studies revealed different NW-substrate interfaces, essential for optimizing the epitaxial growth process. We identified three typical configurations of NW "roots", each impacted by growth conditions and preparation steps, affecting the structural and potentially the optical properties of the NWs. Similarly, doping from the Si-substrate may affect both optical and electrical properties; however, compositional analysis revealed no traces of Si in NWs post-nucleation and a small amount in the catalytic droplet. Our research highlights the importance of in situ studies for a comprehensive understanding of nucleation mechanisms, paving the way for optimizing III-V NW growth on Si substrates and developing high-performance III-V/Si devices.

Buffer-Less Gallium Nitride High Electron Mobility Heterostructures on Silicon.

Thick metamorphic buffers are considered indispensable for III-V semiconductor heteroepitaxy on large lattice and thermal-expansion mismatched silicon substrates. However, III-nitride buffers in conventional GaN-on-Si high electron mobility transistors (HEMT) impose a substantial thermal resistance, deteriorating device efficiency and lifetime by throttling heat extraction. To circumvent this, a systematic methodology for the direct growth of GaN after the AlN nucleation layer on six-inch silicon substrates is demonstrated using metal-organic vapor phase epitaxy (MOVPE). Crucial growth-stress modulation to prevent epilayer cracking is achieved even without buffers, and threading dislocation densities comparable to those in buffered structures are realized. The buffer-less design yields a GaN-to-substrate thermal resistance of (11 ± 4) m2KGW-1, an order of magnitude reduction over conventional GaN-on-Si and one of the lowest on any non-native substrate. As-grown AlGaN/AlN/GaN heterojunctions on this template show a high-quality 2D electron gas (2DEG) whose room-temperature Hall-effect mobility exceeds 2000 cm2V-1s-1, rivaling the best-reported values. As further validation, the low-temperature magnetoresistance of this 2DEG shows clear Shubnikov-de-Haas oscillations, a quantum lifetime > 0.180 ps, and tell-tale signatures of spin-splitting. These results could establish a new platform for III-nitrides, potentially enhancing the energy efficiency of power transistors and enabling fundamental investigations into electron dynamics in quasi-2D wide-bandgap systems.

Time-Dependent Growth of ZnO Nanowires: Unveiling Antibacterial and Photocatalytic Properties.

This study investigates the synthesis, characterization, and functional properties of well-aligned zinc oxide (ZnO) nanowires (NWs) obtained by a two-step hydrothermal method. ZnO NWs were grown on silicon substrates precoated with a ZnO seed layer. The growth process was conducted at 90 °C for different durations (2, 3, and 4 h) to examine the time-dependent evolution of the nanowire properties. A comprehensive characterization of the ZnO NWs was performed using several analytical techniques. Scanning electron microscopy (SEM) revealed the morphological progression, specifically tracking changes in length and diameter as a function of the growth time. Ultraviolet (UV)-visible spectroscopy was employed to determine the optical band gap, while photoluminescence (PL) analysis provided insight into the concentration of structural defects and its evolution as a function of nanowire growth. The photocatalytic efficiency of the ZnO NWs was evaluated through the degradation of the organic dye methylene blue (MB) under UV light irradiation (365 nm). The kinetic of MB degradation was monitored for each growth time, with non-purgeable organic carbon (NPOC) analysis providing a detailed perspective on the photocatalytic activity over time. The antibacterial properties were tested against Pseudomonas putida, a Gram-negative bacterium, to determine the efficiency of the synthesized ZnO NWs as antimicrobial agents. The release of zinc ions (Zn2+), a key factor in the antibacterial mechanism, was quantified using inductively coupled plasma (ICP) analysis for each sample. By exploration of the relationship between the growth time, nanostructure morphology, and functional properties, this study provides insights into optimizing the synthesis of ZnO NWs for enhanced photocatalytic and antibacterial applications. These findings contribute to the development of advanced materials for environmental and biomedical applications.

Oxide layer growth on silicon substrates: effects of temperature and surface preparation

В работе исследуется процесс роста оксидных слоев на кремниевых подложках в контролируемых температурных условиях. Кремниевые пластины окисляли в печи в течение двух часов при температуре от 300°С до 1100°С. Минимальные изменения поверхности наблюдали при температуре ниже 800°C, тогда как при температуре выше 800°C заметные изменения цвета указывали на значительные эффекты окисления. Перед оксидированием кремниевые подложки подвергали тщательной очистке ацетоном, аммиачной перекисью водорода и плавиковой кислотой (HF) с последующей промывкой деионизированной водой. Толщину оксидных слоев измеряли с помощью эллипсометрии. Кроме того, для анализа оксидных слоев использовали инфракрасную спектроскопию с преобразованием Фурье (FTIR). Для каждой температуры получены FTIR-спектры, показывающие данные по поглощению и волновому числу. В частности, мы сосредоточили внимание на оптической плотности в диапазоне от 1000 до 1300 см−1 и изучили ее зависимость от температуры. Наши результаты проливают свет на взаимосвязь между поглощением и температурой, предоставляя ценную информацию о динамике роста оксидного слоя на кремниевых подложках.

Exciton Emission Enhancement in Two-Dimensional Monolayer Tungsten Disulfide on a Silicon Substrate via a Fabry-Pérot Microcavity.

Exciton emitters in two-dimensional monolayer transition-metal dichalcogenides (TMDs) provide a boulevard for the emerging optoelectronic field, ranging from miniaturized light-emitting diodes to quantum emitters and optical communications. However, the low quantum efficiency from limited light-matter interactions and harmful substrate effects seriously hinders their applications. In this work, we achieve a ∼438-fold exciton photoluminescence enhancement by constructing a Fabry-Pérot cavity consisting of monolayer WS2 and a micron-scale hole on the SiO2/Si substrate. The overall enhancement results from the increased exciton-photon interaction due to the effective exciton-cavity mode coupling and decreased trion formation from the weakened substrate effect confirmed by transient spectroscopy. Moreover, the effective coupling improves the directivity of excitons' spontaneous radiation (fwhm ∼ 5°). This research reveals a practical platform for simultaneously enhancing exciton emission and attenuating the substrate effect, and it provides a blueprint for the development of two-dimensional monolayer TMDs-based emitters in integrated optoelectronic devices.

A Microfabrication Technique for High-Performance Diffractive Optical Elements Tailored for Numerical Simulation.

Diffractive optical elements (DOEs) are specialized optical components that manipulate light through diffraction for various applications, including holography, spectroscopy, augmented reality (AR) and virtual reality (VR), and light detection and ranging (LiDAR). The performance of DOEs is highly determined by fabricated materials and fabrication methods, in addition to the numerical simulation design. This paper presents a microfabrication technique optimized for DOEs, enabling precise control of critical parameters, such as refractive index (RI) and thickness. Using photolithography, we fabricated high-precision photoresist patterns on silicon and sapphire substrates, with 3 × 3 and 3 × 5 DOE beam splitter as examples. The results show a strong match between simulation and experimental data, with discrepancies of just 0.53% and 0.57% for DOE on silicon and sapphire substrates, respectively. This approach offers potential for advancing high-performance DOE devices in semiconductor manufacturing, supporting next-generation optical systems.

Biomimetic Silicone Surfaces for Antibacterial Applications.

Biomimetic patterning emerges as a promising antibiotic-free approach to protect medical devices from bacterial adhesion and biofilm formation. The main advantage of this approach lies in its simplicity and scalability for industrial applications. In this study, we employ it to produce antibacterial coatings based on silicone materials, widely used in the healthcare industry. In doing so, we patterned silicone substrates with a topography of various flower petals (rose, chamomile, pansy, and magnolia) and studied the relationship between the antibacterial properties of the obtained biomimetic substrates and their surface topography. To study the surface topography of biomimetic surfaces, we used the fractal analysis of their SEM images. In particular, as a measure of surface complexity and heterogeneity, we used the values of the developed interfacial area ratio (Sdr) and lacunarity coefficient (β). In the result, we found that the bacterial area coverage of biomimetic substrates decreased exponentially with the increase in their surface complexity and heterogeneity, and prominent antibacterial properties were observed at β > 1.6 and Sdr > 50. The results of this study can be used to identify biomimetic materials with superior antibacterial properties and produce efficient antibacterial silicone coatings for biomedical and healthcare applications.

Porous Silicon on Paper: A Platform for Quantitative Rapid Diagnostic Tests.

Porous silicon (PSi) thin films on silicon substrates have been extensively investigated in the context of biosensing applications, particularly for achieving label-free optical detection of a wide range of analytes. However, mass transport challenges have made it difficult for these biosensors to achieve rapid response times and low detection limits. In this work, we introduce an approach for improving the efficiency of molecule transport in PSi by using open-ended PSi membranes atop paper substrates in a flow-through sensor scheme. The paper substrate provides structural support as well as an efficient means of draining solutions from the PSi membrane without the use of an external pump and microfluidic channels. Distinct changes in the reflectance properties of the PSi membrane are measured when molecules are captured in the membrane. A concentration-dependent response of the sensor for protein detection is demonstrated. Factors influencing the interaction time of molecules in the PSi membrane and the drying time of the membrane, which directly affect the detection sensitivity and overall testing time, are discussed. The demonstrated performance of the PSi-on-paper sensor establishes the feasibility of a platform for low-cost rapid diagnostic tests with a highly sensitive, quantitative readout.

Room temperature pure α-phase tantalum films on sapphire for superconducting qubits

Abstract Tantalum (Ta) films with a body-centered cubic (BCC) α-phase play a crucial role in high-performance Ta-based superconducting quantum processors. The growth of pure α-Ta at low temperatures has been a long-term goal. Existing experience with Ta growth on silicon substrates has led to the belief that α-Ta can only be stabilized at high temperatures. In this study, we systematically analyzed the growth mechanism of Ta films on sapphire substrates using first-principles calculations, revealing a narrow growth energy window for pure α-Ta at RT. This finding indicates the feasibility of obtaining pure α-Ta at significantly lower temperatures. Experimentally, we successfully achieved pure α-Ta at RT via magnetron sputtering by meticulously adjusting the growth parameters. The resulting superconducting resonators based on the developed RT α-Ta exhibit an internal quality factor (Q i) of approximately 2.1×106 at single-photon levels, comparable to those fabricated at high temperatures. Additionally, fixed-frequency transmon qubits fabricated using the RT α-Ta film demonstrate a coherence time exceeding 280 μs, underscoring the film’s high quality. The RT α-Ta without a seed layer simplifies the fabrication process, offering a more efficient and flexible approach for producing Ta-based superconducting quantum processors.

Crystal Structure Evolution of Piezoelectric Fe-Doped ZnO Film by Magnetron Co-Sputtering Technique

Zinc oxide (ZnO) exhibits piezoelectric properties due to its asymmetric structure, making it suitable for piezoelectric devices. This experiment deposited Fe-doped ZnO films on silicon substrates using a dual-target magnetron co-sputtering system. The films achieved a high c-axis orientation, and the piezoelectric coefficient of the film reached its optimal value of 44.35 pC/N when doped with 0.5 at% of Fe. This value is approximately three times that of undoped ZnO films with a piezoelectric coefficient of 13.04 pC/N. The study utilized a diffractometer, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy to evaluate the crystal structure evolution of the zinc oxide films and employed X-ray photoelectron spectroscopy to assess the valence state of the Fe ions.

Synthesis of Arsenocholine-Type Polycation Brush and Its Hydration Structure in Aqueous Solution.

Arsenocholine-containing methacrylate (MTAsB) inspired by marine organisms was synthesized by the reaction of 2-bromoethyl methacrylate and trimethylarsine to investigate its polymerization behavior and the fundamental properties of the resulting polymer. Controlled radical polymerization of MTAsB proceeded in the presence of a copper catalyst and imidazolium chloride at 60 °C for 8 h to give a water-soluble polycation with a 94% yield. The smaller amount of nonfreezing water and intermediate water of poly(MTAsB) was observed compared with that of the ammonium-containing polycations. A poly(MTAsB) brush was also prepared on a silicon substrate to investigate its swelling structure in aqueous salt solution by scanning probe microscopy and neutron reflectivity measurements. The brush chains adopted a relatively extended conformation in pure water because of the Coulombic repulsion among the arsenic cation groups of the polyelectrolyte, while the brush formed a collapsed structure in aqueous solutions of Hofmeister series anions as a result of the screening effect by salt ions. In particular, thiocyanate ions induced a significant reduction in the swollen thickness of the brush, probably caused by the attractive interaction between arsenic cations and chaotropic thiocyanate ions. The salt concentration dependency of the poly(MTAsB) brush was similar to that of the ammonium-cation-type polyelectrolyte brushes.

Perturbation-induced nonreciprocal transmission in nonlinear parity-time-symmetric silicon micromechanical resonators

Parity-time (PT) symmetric systems featuring balanced gain and loss, when biased in a broken phase, can produce nonreciprocal transmission in the presence of nonlinear gain. However, the weak coupling in the broken phase leads to high insertion loss during transmission. Here, we demonstrate an approach to achieve nonreciprocal transmission in PT-symmetric silicon micromechanical resonators operating in an exact phase. In our approach, PT-symmetry breaking due to external perturbations to the loss resonator results in exponential growth and decay modes. The presence of the nonlinear gain suppresses the exponential growth mode. As a result, the nonreciprocal transmission is achieved while keeping the system at the strong coupling region. The coupling strength, perturbation, and gain nonlinearity of the system can be electrically tuned. The system shows 8 dB of nonreciprocal transmission with the insertion loss less than 5 dB and the isolation more than 13 dB. Our approach demonstrates the ability to manipulate nonreciprocal transmission and opens a door towards the development of electronic isolators and circulators on silicon substrate.

Recycling of Photovoltaic Modules – A Strategy for Silicon and Metal Contact Recovery

As the installed capacity of photovoltaic (PV) systems continues to grow, also does the necessity to address the accumulating waste from decommissioned PV modules. Millions of modules will need to be retired in the next few decades, and this poses a challenge that requires the development of cost-effective and efficient recycling strategies, with a focus on essential components such as solar cells, which are known for their significant environmental impact and energy budget. This study explores strategies to recover metal from front and rear contacts, as well as the potentiality of silicon substrate recrystallization. Alkaline-organic solutions allow for complete metal detachment with small-to-minimal silicon loss, and recrystallization of recovered substrates provides promising results in obtaining wafers suitable for the newly established industry requirements. Al-BSF solar cells fabricated from recycled materials exhibit improved performance, proving the feasibility of reclaiming precious metals and silicon substrates from PV modules. These encouraging first results represent an important step towards cycling PV systems within a circular economy framework, thereby minimizing waste and maximizing resource utilization.

Microwave plasma-enhanced chemical vapor deposition growth of graphene nanowalls on varied substrates: A comparative study

We explored the growth rate and morphological characteristics of graphene nanowalls (GNWs) on copper (Cu), stainless steel (SUS), quartz and silicon (Si) substrates by changing the growth time using microwave plasma-enhanced chemical vapor deposition (MWPCVD). Furthermore, we investigated the impact of catalytic and non-catalytic substrates on the growth features of GNWs. The properties of GNWs were characterized using scanning electron microscopy (SEM) and Raman spectroscopy. The growth of GNWs occurred just after supplying the precursor on the Cu substrate, but those on SUS, quartz and Si delayed about 5 min, 10 min and 15 min, respectively, due to the low catalytic activity of the substrate. Once the growth started, there was not much of a difference in the growth rate. The average growth rate was about 2 nm/s. The crystallinity of GNW was improved with increasing growth time. It was found that Cu is the best substrate to get high-quality GNWs, but MWPCVD is a suitable technique to obtain GNWs on a variety of substrates at relatively low temperatures.