Silicon Wafers Research Articles

Highly 28Si enriched silicon by localised focused ion beam implantation

Solid-state spin qubits within silicon crystals at mK temperatures show great promise in the realisation of a fully scalable quantum computation platform. Qubit coherence times are limited in natural silicon owing to coupling to the 29Si isotope which has a non-zero nuclear spin. This work presents a method for the depletion of 29Si in localised volumes of natural silicon wafers by irradiation using a 45 keV 28Si focused ion beam with fluences above 1 × 1019 ions cm−2. Nanoscale secondary ion mass spectrometry analysis of the irradiated volumes shows residual 29Si concentration down to 2.3 ± 0.7 ppm and with residual C and O comparable to the background concentration in the unimplanted wafer. After annealing, transmission electron microscopy lattice images confirm the solid phase epitaxial re-crystallization of the as-implanted amorphous enriched volume extending over 200 nm in depth.

Peculiarities in XPS spectra of Sn/SiO2 layers as an effect of surface charge

X-ray photoelectron spectroscopy based on synchrotron radiation was used to investigate the composition of the observed SnO2-x/Sn:SiO2-x thin layer grown by organometallic chemical vapour deposition on single-crystalline silicon wafer with additional argon ions etching treatment. Due to the formation of a thermodynamic anomaly during in situ layer growth, an efficient oxygen exchange between silicon and tin oxide phases occurs. The present study addresses the effect of localized surface charging and its influence on the obtained XPS core level spectra. We found that due to the high electrical conductivity of metallic tin and the direct coupling of tin particles to the silicon wafer, the XPS Sn 3d5/2 core level spectrum is not affected by the surface charge compared to the highly charged dielectric silicon oxide matrix, as observed for the XPS O 1 s and Si 2p core level spectra. Our results show that the core level spectra of Si 2p and O 1 s are shifted up to 3 eV due to the presence of uncompensated positive charge on the surface of the silica matrix. These results provide insight into the influence of surface charge effects on the analysis of conductor/insulator composite materials and contribute to the application of Sn-based materials in various application concepts related to energy and surface functionalization.

Model for surface topography prediction in the ultra-precision grinding of silicon wafers considering volumetric errors

Ultra-precision grinding machine is widely used for thinning silicon wafers. The wafer surface quality is considerably affected by volumetric errors at the functional point of the ultra-precision grinding machine. Therefore, a volumetric error model is established based on the homogeneous transformation matrix (HTM) method. The model is, then, optimized by considering Abbe and Bryan errors induced volumetric errors during the error measurements process. A prediction model for the wafer surface topography is established by combining the manufacturing mechanism of the ultra-precision grinding and the optimized volumetric error model of the ultra-precision grinding machine. Volumetric errors are detected using an author’s group developed laser measurement system and a commercial spindle error analyzer. The model enables to predict the topography and total thickness variation (TTV) of the wafer surface. A group of grinding experiments are performed to verify the effectiveness of the proposed models.

Anisotropy of the conductivity of silicon nanowires

ABSTRACT This study reports the findings from an investigation into charge carrier transport within a silicon nanowire layer. The samples were prepared using the metal-assisted chemical etching method applied to crystalline silicon wafers with a resistance of 10–20 Ω·cm. The resulting silicon nanowires had a diameter of about 100 nm with a resistance of approximately 15 kΩ·cm. Electrical conductivity measurements were performed in both planar and sandwich configurations, revealing analogous conductivity mechanisms across different geometries. Frequency-dependent conductivity studies unveiled the presence of hopping conductivity. A hypothesis is proposed regarding the existence of a potential barrier at the interface between the nanowire layer and the substrate.

Optimization of bulk microdefect performance in epitaxial silicon wafer

Bulk microdefects (BMDs) in epitaxial silicon wafers are pivotal for advanced node integrated circuits, offering enhanced mechanical strength and metal gettering capabilities. This study introduces two heat treatment procedures to optimize BMD density and radial uniformity in lightly doped wafers, addressing the challenges associated with large-diameter crystal growth and the thermal budget constraints of advanced node processes. We demonstrate that Rapid Thermal Annealing (RTA) at temperatures exceeding 1175 °C significantly improves BMD uniformity. A post-RTA stabilization step, when performed prior to epitaxial growth, enhances BMD density by retaining nuclei generated by RTA. Conversely, when the RTA with stabilization step follows epitaxial growth, a higher BMD density and larger BMD size are achieved. Light Scattering Tomography (LST) analysis confirms the optimal conditions for these treatments. The findings contribute to the semiconductor industry by optimizing wafer properties for high-performance ICs.

Surface topography and subsurface structure evolution in laser micro polishing of monocrystalline silicon

Ultra-smooth silicon surfaces, crucial in short-wave optics, can be marred by surface defects and subsurface damage incurred during machining, thereby affecting the imaging quality and transmission efficiency of optical components. Laser micro-polishing emerges as a versatile and efficient technique for ultra-precision polishing. This study aims to scrutinize the surface topography and subsurface structural evolution of monocrystalline silicon wafers during laser micro-polishing experimentally and to formulate an accessible evaluation model that incorporates multiple process parameters for optimal polishing results. As laser fluence escalates, the polishing process can be divided into six regimes: bulge, coalescence, smoothness, groove, ripple, and ablation. Each regime's crystal structure evolution is analyzed using Raman spectroscopy, demonstrating a close relationship with the surface expansion preceding the melting of monocrystalline silicon. Surface roughness diminishes from 6 nm to 0.7 nm, and an optimal crystalline quality devoid of an amorphous layer, residual stress, or significant subsurface damage is achieved. Amorphous silicon, 20 μm thick, is converted into monocrystalline silicon through recrystallization, and subsurface distortions and dislocations are rectified due to silicon atom redistribution. Moreover, a mapping relationship between multiple process parameters and surface polishing effects is established. A dimensionless fluence considering multiple parameters is derived, and a predictive model for process parameter optimization to secure optimal polishing results is proposed.

Light-triggered defect dynamics in silicon wafers: understanding degradation mechanisms

Light-triggered defect dynamics in silicon wafers: understanding degradation mechanisms

Titanium dioxide/nitrogen-doped graphene-biopolymer based nanocomposite films for pollutant photodegradation and laser desorption ionization mass spectrometry of biomarkers

Titanium dioxide (TiO2)/nitrogen-doped graphene (NG) nanocomposite is prepared via a solvent-free hydrothermal reaction. The resulting TiO2/NG materials exhibit a reduction of the band gap energy compared to pristine TiO2 from 3.27 eV to 2.69 eV. These materials are characterized by scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). To prepare biopolymer films with photocatalytic properties, TiO2 and NG are mixed with biodegradable chitosan and spin-coated on a silicon wafer. Film roughness and thickness are evaluated by atomic force microscopy (AFM). These films are then tested for ciprofloxacin photodegradation by irradiating with visible light. In comparison to the TiO2/chitosan films, the addition of NG substantially enhances photodegradation efficiency by up to 34 % upon the addition of 5 % w/w of NG. Furthermore, this film is shown to be a good substrate for biomarker detection using laser desorption ionization mass spectrometry (LDI-MS). In summary, this nanocomposite-biopolymer film provides good photocatalytic activity towards ciprofloxacin degradation and enhances the ionization efficiency of peptide biomarkers in LDI-MS owing to high efficiency of laser absorption/desorption. This nanocomposite film might be useful for environmental-related and medical application.

Cover Image, Volume 62, Issue 9

By adjusting the concentration of the solution of hyperbranched poly(o‐hydroxyamide)s and spin‐coating the solution on a silicon wafer, the ultrathin films could be obtained. After heating, the obtained ultrathin films could be converted to the corresponding polybenzoxazole ultrathin films, which have high thermal stability, good durability, and toughness. They are expected to find applications in various fields in the near future. The cover design was created by the first author, Mr. Hiroyuki Maekawa. DOI: 10.1002/pol.20230659 image

Advanced ice lithography system using a micro-machined Joule-Thomson cooler

This study introduces a novel ice lithography system integrated with a low-vibration micro-machined Joule-Thomson cooler. Ice lithography is an eco-friendly method for high-resolution nanofabrication on delicate substrates and requires to operate below 130 K in the vacuum of a microscope chamber. Previously, liquid nitrogen rather than cryocoolers was used to cool the system due to its low vibration, but it is both bulky and costly. To overcome these challenges, this study employs a low-vibration micro-machined cooler in a scanning electron microscope (SEM) for ice lithography. The design and methodology of the system are described in detail. The results show that the substrate can reach a temperature of 105 K within 30 minutes with a measured mechanical vibration of less than 10 nm, enabling high-resolution nanofabrication. As proof of concept, the system successfully fabricates nanoscale patterns on a silicon wafer. This low-vibration cooling system has great potential for use in cryogenic electron microscopes (cryo-EMs) in the future.

Emission of ions and electrons correlated with soft and hard x-rays evolution from thermal plasma

This paper presents a correlation between time evolution of ions and electrons with soft and hard x-rays emitted from argon plasma. The plasma setup comprises of two copper electrodes connected with a dc power supply. Faraday cups were used to monitor time evolution of ions, to extract their energy, temperature, and flux. Double Langmuir probe was employed to determine electron temperature, energy, and density. To explore time-resolved emission of soft x-rays, PIN photodiodes filtered with 24 μm aluminum, 90 μm Mylar, 80 μm copper, and 10 μm silver have been used. To evaluate temporal evolution of hard x-rays, a scintillator–photomultiplier system was utilized. The plasma was generated using argon gas at atmospheric pressure 760 Torr and constant flow rate 5 L/min at 7, 9, and 11 kV. The flux, energy, and temperature of Ar ions increase with the increase in the operating potential. Soft x-ray signals last much longer (3000 ns) than those of electrons' and ions' signals (300 ns). The plasma operated at 11 kV permits highest emission of ions, electrons, and x-rays. The ions, electrons, and hard and soft x-ray irradiation on silicon wafer exhibited the presence of damaged trails. Ion irradiation showed the presence of latent damaged trails. Electron irradiation caused more damage to the Si surface compared to ion irradiation due to higher flux and density. Soft x-rays had a lesser effect as compared to Si exposed to hard x-rays due to higher energy of the hard x-rays. In the case of hard x-rays irradiated Si, erupted volcano-like structure is formed.

Generation and Applications of a Broad Atomic Oxygen Beam with a High Flux‐Density via Collision‐Induced Dissociation of O2

Generation and Applications of a Broad Atomic Oxygen Beam with a High <scp>Flux‐Density</scp> via <scp>Collision‐Induced</scp> Dissociation of <scp>O₂</scp>

The growth and characterization of Au-catalyzed gallium oxide nanowires

AbstractGallium oxide is a powerful and versatile wide band gap semiconductor, which has been gaining scientific interest in recent years due to its applications in power electronics. In this work, the growth of β-gallium oxide (Ga2O3) nanowires has been achieved by the vapor–solid–liquid method on silicon wafer, fused quartz, and gallium oxide thin-film substrates. In a chamber purged of ambient atmosphere, pure gallium was heated to produce gallium vapor, which was then oxidized by minute oxygen impurities in the backing gas to form gallium oxide nanowires on a substrate, inside a vertical tube furnace. On the silicon wafer substrates, β-Ga2O3 nanowires were observed to grow in a specific crystallographic direction via transmission electron microscopy. The resulting nanowires were highly faceted and had a unique polyhedral structure on the gold catalyst ‘cap’ of the nanowire. Time of growth and oxygen-level studies were conducted on nanowires grown on various substrates. Graphical abstract

One step synthesis of durable slippery, oil/water selective, corrosion-resistant silicone coatings with grafted flexible sidechains

Slippery liquid-infused porous surfaces (SLIPSs) based on polymer matrices impregnated with liquid lubricants are multifunctional and provide a wide range of useful properties such as low adhesion of water and other liquids, selectivity, high corrosion resistance, etc. However, these properties vanish quickly due to the gradual depletion of lubricant from the matrix. This issue could be resolved by attaching lubricant molecules to the matrix as flexible, liquid-like sidechains. In the present work, thin silicone films with grafted sidechains are fabricated. The uniform coatings are obtained in “eco-friendly” pressurized (subcritical) CO2 on smooth silicon wafers as well as on rough porous substrates such as carbon aerogels. The possibility of applying films by the traditional dip-coating method is also demonstrated on titanium slides. The coatings demonstrate low sliding angles for water and water/alcohol solution droplets. Coated aerogels preserve high porosity. It is demonstrated that initially hydrophilic aerogels become highly hydrophobic after coating and selectively absorb oil from water/oil mixtures. The tests of obtained coatings on titanium substrates demonstrate a significant increase in corrosion resistance. The proposed technique has a wide range of potential applications where such slippery coatings should be applied on complex rough substrates: from filtration materials production to textile finishing.

A healable amino silane self-assembled monolayer incorporating polymer capped palladium nanoclusters and its application as the copper diffusion barrier layer on silicon wafer

Self-assembled monolayers (SAMs) with short organic chains terminated with specific functional groups are attractive for modifying surface properties for a variety of applications, including being a copper diffusion barrier layer on Si wafer. However, SAM formation is process-sensitive and ideal SAM is difficult to obtain, both of which need to carefully deal with before practical use. Herein we developed a system to achieve seamless electroless deposited copper (ELD Cu) film on an amino-terminated silane SAM modified Si wafer with the help of a bifunctional polyvinyl alcohol-capped Pd nanocluster (PVA-Pd) catalyst. The PVA-Pd acts as a catalyst for ELD Cu as well as a healing agent to fix defects of the amino silane SAM. The sheet resistance, cross-sectional morphology analysis and adhesion of ELD Cu on the Si wafer are extensively studied. By controlling the abundancy of PVA in PVA-Pd, the diffusion barrier property of a flawed amino-terminated silane SAM remains reliably effective even after a 500 °C rapid thermal annealing (RTA), evidencing the superior healing function of PVA. The whole thickness of the PVA-Pd/amino-terminated silane SAM before and after RTA is 〜6 nm and 〜2 nm, respectively, which is applicable for advanced microelectronic manufacturing.

Significance of heat generation and thermophoretic particle deposition in Marangoni convective driven boundary layer flow of cross nanofluid with activation energy

The thermo-solutal Marangoni boundary layer flow has been studied because it has a number of real-world uses, such as drying silicon wafers, applying thin coats of paint or glue, employing adhesive in heat exchangers, and growing crystals in space. The physical phenomenon of Cross (FeSO4−(CMC−H2O(<0.4%)) nanofluid flow in a porous medium with thermophoretic particle deposition and Marangoni convective flow is explored. Non-Newtonian Cross nanofluid flow is explored in relation to the effect of activation energy. The process of thermophoretic particle deposition, which is important in both electrical engineering and aero-solution, is one of the most fundamental methods for transferring small particles across a heat gradient. Cross nanofluid containing FeSO4 as nanoparticle, and based fluid is (CMC- water). Using the appropriate similarity variables, the set of governing PDEs is transmuted into a set of ODEs. The RKF-45th method is used to numerically solve these simplified equations. The graphic examination of the concentration, velocity and thermal fields is developed for the embedded non-dimensional characteristics. By raising the Marangoni ratio parameter, the surface tension gradient gets stronger, causing the induced flows to get stronger through the liquid more effectively. The concentration and thermal profiles fall with an enhancement in Marangoni ratio parameter.

Remarkably improved cycling stability of commercial micron-sized silicon enabled by a novel organic/inorganic hybrid binder

Silicon (Si) anode with ultra-high capacity and low cost are highly desirable for next-generation high-energy lithium-ion batteries, whereas suffers from severe volume change that causes rapid capacity decay upon lithiation/delithiation. The development of high-performance binders to alleviate volumetric expansion and maintain integrity of Si particles remains a significant challenge. Here, reported is a novel organic/inorganic hybrid binder composed of partial neutralized polyacrylic acid (PAAS) and sodium metaborate tetrahydrate (SMTH), which achieves in-situ crosslinking upon drying wafer electrodes. The robust crosslinked network structure with borate ester bonds is successfully attained, and can be modulated by changing the content of sodium metaborate. The strong covalent bond network endows the hybrid binder system with superior mechanical properties and powerful adhesion, which improve the contact and integrity of wafer silicon electrode by suppressing volume expansion and exfoliation, therefore facilitating Li-ion migration and enhancing electrochemical performance. The resulting commercial micro-silicon wafer electrode with PAAS/0.08SMTH binder remains a reversible specific capacity of 1670 mAh g−1 after 150 cycles at 300 mA g−1, largely superior to that prepared with the original PAAS binder because its reversible specific capacity was determined to be only 1046 mAh g−1 under identical conditions. The in-situ crosslinked 3D network structure provides a facile feasible way to improve the high-capacity anode materials for lithium-ion batteries.

Fabrication of Ordered Macropore Arrays in n-Type Silicon Wafer by Anodic Etching Using Double-Tank Electrochemical Cell.

In this work, ordered macropore arrays in n-type silicon wafers were fabricated by anodic etching using a double-tank electrochemical cell. The effects of the wafer thickness, etching time and voltage on the quality of macropore arrays were investigated. Homogeneous macropore arrays could be achieved in 200 μm thick silicon wafers, but could not be obtained from 300 and 400 μm thick silicon wafers. Highly ordered macropore arrays with an aspect ratio of 19 were fabricated in 200 μm thick n-type silicon at 4.5 V. The etching current decreases in 200 μm thick silicon but increases in thicker silicon with an increase in time. It demonstrates that the minority carrier transportation capability from the illuminated surface to the reactive surface is different for silicon wafers with different thicknesses. The minority carrier concentration at the illuminated surface for stable macropore formation and the current under different etching voltages were calculated based on a hole transport model. The results show that appropriately decreasing wafer thickness and increasing voltage can help stable macropore array fabrication in the illumination-limited double-tank cell.

Qualification of Microwave SQUID Multiplexer Chips for Simons Observatory

The Simons Observatory is a cosmic microwave background experiment stationed atop Cerro Toco, at an elevation of 5200 ms in Chile’s Atacama Desert. The receivers of the Observatory will contain more than 60,000 transition edge sensor bolometers. In order to read out this large detector count in a scalable manner, we utilize a microwave superconducting quantum interference device (SQUID) multiplexing scheme where each detector is inductively coupled to an rf SQUID, which in turn is inductively coupled to a GHz resonator. More than 2000 SQUIDs and resonators are fabricated on a single 76.2-mm-diameter silicon wafer. To qualify wafers before integration, we cryogenically screen ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document} 10% of the devices on each wafer by use of a standard set of measurements. From these data, we report parameter value trends in 47 wafers that were fabricated in the past two years. We show good control in key parameters such as frequency placement, internal quality factor, and response to applied flux. We demonstrate a wafer acceptance yield of 86%.

Investigation of Field Emission Properties of Carbon Nanotube Arrays of Different Morphologies.

This article presents, for the first time, a comparative analysis of the emission characteristics of large-area field-effect cathodes (LAFE) based on carbon nanotubes (CNTs) of various morphologies according to key parameters using a unique computerized technique. The work presents a description of a technology for creating various CNT arrays and their comprehensive structure characterization. All CNT arrays synthesized by the catalytic PECVD method on a silicon substrate showed a high degree of chemical purity under the presented technological conditions. In some cases, nanoisland films of Fe were used as a catalyst; in others, thin films of NiO were used, which were deposited on a silicon wafer by chemical vapor deposition (CVD) and atomic layer deposition (ALD), respectively. As a result of these studies, it turned out that an array with a thick CNT coating has good resistance to the action of strong electric fields, fairly good uniformity of distribution of emission centers, a fairly high selection current (2.88 mA/cm2 at 4.53 V/μm), and compliance with the normal current mode according to the "orthodox" test, which makes the morphology of such structures the most promising for further technological optimization of CNT-based cathodes for various practical applications.