Single Crystal Silicon Wafers Research Articles

Nanostructured boron-doped diamond electrodes for two-electron water oxidation to produce hydrogen peroxide

Boron-doped diamond (BDD) electrodes have been widely used in water treatment, e.g., degradation of antibiotics and pigments for water purification. Hydrogen peroxide production by two-electron electrochemical oxidation of water is a green and attractive method that has the potential to replace the conventional anthraquinone autoxidation (AO) process. In this study, BDD films were prepared on single-crystal silicon wafers by using hot-filament chemical vapor deposition (HFCVD) technique. Then, dense tubular nanostructure (nanotubes) arrays were prepared on the BDD films employing inductively coupled plasma (ICP) etching. Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) proved the formation of oxygen-terminated nanostructures, which was ascribed to the oxygen plasma and the self-masking. The length of diamond nanotubes as well as the root diameter increased gradually and non-linearly with the increase of etching time. It was indicated by cyclic voltammetry (CV) analysis that the effective active area of the electrodes increased after etching, and variations of resulting reaction performance were observed. The oxygen-terminated and nanostructured BDD electrode obtained by etching with the optimized parameters features better electrocatalytic performance, with reduced oxidation potential and 46.8 % higher Faraday Efficiency (FE) for hydrogen peroxide production, compared to the original BDD sample. Therefore, the manufacturing of nanostructures is an effective method to improve the efficiency of BDD water oxidation for the production of hydrogen peroxide.

Analysis Of Silicon Crystal Materials: Meeting Growing Demands Across Industries

The demand for silicon crystal materials is poised for continued growth across diverse sectors in the upcoming years. In the realm of computers and communication, silicon single crystal wafers and chips are in high demand, fueled by the increasing adoption of communication equipment and the essential requirement for memory and control chips in information processing systems. Beyond the electronics domain, silicon crystals find applications in various industries, including environmental protection, new energy, and construction. In the field of environmental protection, silicon crystals play a vital role in denitrification and dust removal devices. In the new energy sector, they contribute to solar photovoltaic power generation systems and geothermal power generation systems. In construction, silicon crystals find their place in the production of building glass and semiconductor building materials. As China's economy continues to evolve and environmental concerns gain prominence, the demand for semiconductor materials, including silicon crystal materials, is anticipated to rise. This underscores a bright market outlook for silicon crystal materials in the foreseeable future.

Dynamic magnetic field magnetorheological finishing with constant load and variable gap

Magnetorheological finishing is limited by weak polishing forces and small polishing areas, resulting in a low polishing efficiency. This study formulates a method for dynamic magnetic field magnetorheological finishing in compression-shear mode with a constant load and variable gap, which can remodel the magnetic particle string using a dynamic magnetic field and enhance the polishing force by a constant load and variable gap. To investigate the impact of process parameters on macro and micro machining processes, as well as their effects, a series of experiments were conducted to investigate the polishing force, machining clearance, and machining effect of single-crystal silicon wafers under four different conditions: static magnetic field magnetorheological finishing (T1), dynamic magnetic field magnetorheological finishing (T2) at a constant gap, static magnetic field magnetorheological finishing (T3), and dynamic magnetic field magnetorheological finishing (T4) with a constant load and variable gap. The results indicated that the shearing force and processing quality significantly improved in the constant-load and variable-gap modes, and the process of machining clearance reduction involved two stages: fast and slow compression. The shearing force of T3 increased by 35 % compared to T1, and T4 increased by 20 % compared to T2. The material removal rate of T3 and T4 increased over time, in contrast to those of T1 and T2. The key parameters of the T4 single-factor shear and machining gap testing experiments show that the constant load variable gap compression process adaptively adjusts the machining gap such that the chain string structure is in a body-centered cubic structure (BCT), increasing the number of abrasive contacts and the depth of pressure into the workpiece to achieve a significant increase in the polishing shear constant load.

Beating resonance patterns and extreme power flux skewing in anisotropic elastic plates.

Elastic waves in anisotropic media can exhibit a power flux that is not collinear with the wave vector. This has notable consequences for waves guided in a plate. Through laser-ultrasonic experiments, we evidence remarkable phenomena due to slow waves in a single-crystal silicon wafer. Waves exhibiting power flux orthogonal to their wave vector are identified. A pulsed line source that excites these waves reveals a wave packet radiated parallel to the line. Furthermore, there exist precisely eight plane waves with zero power flux. These so-called zero-group-velocity modes are oriented along the crystal's principal axes. Time acts as a filter in the wave-vector domain that selects these modes. Thus, a point source leads to beating resonance patterns with moving nodal curves on the surface of the infinite plate. We observe this pattern as it emerges naturally after a pulsed excitation.

Controlling adhesion and thermal stability of tetrahedral amorphous carbon coatings with intermediate sp3C fraction

Tetrahedral amorphous carbon (ta-C) coatings with an intermediate sp3C fraction were deposited on single-crystal silicon wafer substrates via intermittent filtered cathode vacuum arc (FCVA) deposition. The ta-C layer thickness and sp3C fraction in the coatings were adjusted using the deposition duration and bias voltage applied to the substrate, respectively. Some of the coated specimens were annealed at 300 and 600 °C for 4 h in a 5-Pa vacuum. The morphologies and microstructures of the specimens were characterized using scanning electron microscopy and transmission electron microscopy. The hybridization of carbon atoms was analyzed using X-ray photoelectron spectroscopy and micro-Raman spectroscopy. The mechanical characteristics of the coatings, including the critical adhesion load between the coatings and substrates, residual stress in the coatings, and hardness, were characterized. For the specimens deposited by the same bias voltage, even their top ta-C layer thickness ranged from approximately 500 nm to 1500 nm, their residual compressive stress in the coatings was maintained at a low value by the intermittent deposition of FCVA, which varied slightly with the coating thickness. The adhesion strength was improved by increasing the thickness of the as-deposited coating from approximately 12 to 40 N. The residual compressive stress of the post-annealing specimens with sp3C fraction of 45–53.8 % exhibited monotonously increasing or V-shaped variation with increasing annealing temperature. Herein, the underlying mechanisms are discussed in detail.

Hierarchical Structuring of Black Silicon Wafers by Ion-Flow-Stimulated Roughening Transition: Fundamentals and Applications for Photovoltaics.

Ion-flow-stimulated roughening transition is a phenomenon that may prove useful in the hierarchical structuring of nanostructures. In this work, we have investigated theoretically and experimentally the surface texturing of single-crystal and multi-crystalline silicon wafers irradiated using ion-beam flows. In contrast to previous studies, ions had relatively low energies, whereas flow densities were high enough to induce a quasi-liquid state in the upper silicon layers. The resulting surface modifications reduced the wafer light reflectance to values characteristic of black silicon, widely used in solar energetics. Features of nanostructures on different faces of silicon single crystals were studied numerically based on the mesoscopic Monte Carlo model. We established that the formation of nano-pyramids, ridges, and twisting dune-like structures is due to the stimulated roughening transition effect. The aforementioned variety of modified surface morphologies arises due to the fact that the effects of stimulated surface diffusion of atoms and re-deposition of free atoms on the wafer surface from the near-surface region are manifested to different degrees on different Si faces. It is these two factors that determine the selection of the allowable "trajectories" (evolution paths) of the thermodynamic system along which its Helmholtz free energy, F, decreases, concomitant with an increase in the surface area of the wafer and the corresponding changes in its internal energy, U (dU>0), and entropy, S (dS>0), so that dF=dU - TdS<0, where T is the absolute temperature. The basic theoretical concepts developed were confirmed in experimental studies, the results of which showed that our method could produce, abundantly, black silicon wafers in an environmentally friendly manner compared to traditional chemical etching.

Cutting force modeling and control of single crystal silicon using wire saw velocity reciprocation

Single crystal silicon wafers are often used as substrate material for integrated circuits. Often the wafer is cut by a wire with fixed abrasive diamond owning to a narrow kerf and a low cutting force. The cutting force changes during the process as the direction of wire movement continuously reverses (i.e., reciprocates), which may cause the wire saw to break, the wafer to collapse, and the wafer surface roughness to decrease even if the wire saw tension and the contact length between the wire and the wafer are fixed. In this work, a cutting force model including both normal and tangential forces was established to determine the relationship between the normal and tangential forces and the commanded wire speed. Separate controllers were developed to regulate both the normal force and the tangential force by adjusting the wire velocity. Experimental studies were conducted for wire saw processing of single crystal silicon wafers. Compared with a process using constant wire velocity, regulating the normal force can significantly reduce the processing time and the wafer surface roughness. The average improvements in processing time and wafer surface roughness are approximately 11% and 56%, respectively, when using normal force control, and approximately 29% and 30%, respectively, when using tangential force control. The results show that the normal and tangential forces can be well regulated during the machining process. In addition, the wafer surface roughness and machining time were lower in both experiments where the forces were regulated than in the experiment where a constant wire velocity was used. This paper demonstrates that the novel concept of regulating process forces in wire saw machining by adjusting the wire velocity can be used to optimize the cutting process of single crystal silicon, making the process more productive while decreasing the part roughness.

Confirmation of n‐Hexane as an Inert Co‐Solvent in the Production of Functionalized Silicon Nanoparticles from Reactive High‐Energy Ball Milling

AbstractAlkanes such as n‐hexane have been used as co‐solvents in the production of functionalized semiconductor nanoparticles from alkenes and alkynes using Reactive High Energy Ball Milling (RHEBM) under the assumption that they are non‐reactive under typical milling conditions. In this paper, a comparative study with two hydrocarbon solvents of comparable chain length, 1‐hexyne, and n‐hexane, and their milling products using three different commercially available silicon precursors, namely single crystal silicon wafers and polycrystalline particles having a nominal size of 4 µm and 1 mm, is reported. It is found that nanoparticle formation and surface functionalization in all the three silicon systems occurs only with 1‐hexyne; n‐hexane is non‐reactive and does not lead to appreciable functionalized nanoparticle formation under the conditions studied. Nanoparticles (where formed) and microparticle byproducts of appropriate samples are characterized by Transmission electronic microscope (TEM), Fourier transform infrared (FTIR), Photoluminiscence spectroscopy (PL), Nuclear magnetic resonance 1H/13C NMR, and thermogravimetry TGA to separately confirm nanoparticle formation and surface functionalization.

Influence of Structural Defects on the Electrophysical Parameters of pin-Photodiodes

The results of studies of electrophysical parameters of pin-silicon-based photodiodes, depending on their operating modes (external bias and temperature), manufactured on single-crystal silicon wafers of p-type conduction orientation (100) with ρ = 1000 ohm cm, are presented. The p+-type region (isotype junction) is created by the implantation of boron ions; the n+-type region, by the diffusion of phosphorus from the gas phase. It is established that on the voltage-current characteristics under reverse bias, three regions of dark cur-rent variation depending on the applied voltage can be distinguished, sublinear, superlinear, and linear, caused by various mechanisms of the generation-recombination processes in the depletion region of the pn-junction. A noticeable dependence of the barrier capacitance value (at a frequency of 1 kHz) and the size of the depletion region on temperature is observed only when the applied reverse voltages do not exceed the contact potential difference (V ≤ 1 V).

Mechanically Coupled Single-Crystal Silicon MEMS Resonators for TCF Manipulation

This paper presents mechanically coupled single-crystal silicon (SCS) microelectromechanical system (MEMS) resonators for temperature coefficient of frequency (TCF) manipulation. The reported mechanically coupled square extensional (SE) mode resonator consists of two square plates coupled with a beam or a third square plate purposely vibrating in another bulk mode. The SE mode resonators and the coupled structure can be considered as two kinds of individual resonators with different TCFs. Within the specific dimensions of the coupled resonator, the resonant frequencies of the two components are assumed to be equal. Hence, the TCF of the mechanically coupled resonator could be manipulated by adjusting the sizes of the coupling parts. The design and fabrication of coupled resonators have been completed in a degenerate-doped (100) SCS wafer. Measurement results illustrate that the TCFs of the coupled resonators can be purposely manipulated by adjusting the volume and equivalent spring constant ratios of the individual resonators. The minimal measured frequency shift is roughly <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 10 ppm for an 18 MHz coupled SE mode resonator, over the entire industrial temperature range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 40 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> C to 85 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> C. This work highlights a novel and effective way to manipulate the TCFs of MEMS resonators via mechanical coupling. 2022-0197

A realistic assessment of the prospect of silicon be replaced by other materials for IC applications

Silicon is the most common material used in semi-conductor. It can be used to make single crystal silicon wafer. Though it has the widest usage, silicon has high calorific value. Also, the performance loss is high compared to silicon carbide and the operating temperature is relatively low compared to gallium oxide. Luckily, there are several materials that could possibly replace silicon. The first one is 2D semiconductor. The prospective evaluation of 2D semiconductors is high. But now the biggest problem is the low-resistance connections with them. The second one is gallium nitride. It has high hardness, melting point and stability. This makes it a good material for high temperature, high frequency and high power devices. However, excellent property brings high cost. This disadvantage prevents gallium nitride to be widely used. The last one is graphene. It has strong electrical conductivity, ultra-high strength, excellent electrical properties, and strong electron interaction. It has a higher carrier mobility than silicon. While every coin has two sides, producing graphene on a large scale is difficult and expensive. Besides, graphene is highly reactive with oxygen and heat. What’s more, zero band gap nearly makes it impossible to become a semi-conductor material. Even though there are many methods of opening the bandgap, these methods still bring inevitable drawbacks. All in all, there are still many problems to be solved when new materials replace silicon in integrated circuit applications.

Metallization system as a part of thermal memory

This study aims to substantiate the potential of using “classical” metallization systems as microelectronic thermal memory cells. An experimental simulation is used to demonstrate that thermal information can be stored in memory for a certain time and then read without distortion. The possibility of using thin metal films on single-crystal silicon wafers as thermal memory cells is discussed. An experimental parametric study of “recording” thermal pulses and the temperature dynamics after their interruption is performed. This study uses rectangular current pulses with an amplitude of (1 … 6) × 1010 A/m2 and a duration of up to 1 ms. The temperature dynamics of a “thermal cell” are oscillographically studied up to the critical conditions when the contact area and metal film start degrading. The conditions of interconnections overheating up to the circuit break are considered.

Microscopic stress analysis of nanoscratch induced sub-surface defects in a single-crystal silicon wafer

The existing stress criterion assumes the material to be isotropic and only distinguishes elastic, plastic, and crack zones, to explain the scratching-induced sub-surface defects during the contact loading processes such as nanoindentation, nanoscratching, and grinding. However, anisotropic single-crystal materials such as monocrystalline silicon and silicon carbide have more diverse defect characteristics and sub-surface defects in these materials cannot be well explained and predicted using the existing criterion. In this study, a thorough microscopic characterisation and complementary stress analysis were performed on a single-crystal silicon wafer during nanoscratching. A novel criterion based on mechanism of dislocation multiplication and propagation was proposed and validated, providing a better understanding of sub-surface defects prediction in silicon. Compared to conventional sub-surface defects models, this new shear stress-based criterion can accurately predict the position and extent of dislocations in silicon. The dislocations layout for scratching along any direction on the (100) surface of Si were further discussed to offer a comprehensive understanding of the effect of anisotropic structure of single-crystals on the sub-surface defects. The improved understanding of inelastic deformation in single-crystal silicon, which was revealed by this new model, will have a significant impact on the nanomanufacturing sector by guiding the contact mode experiments (grinding, indentation, machining) towards efficient machining.

Investigation of the Angle of Sliding a Drop of Water from the Surface of the SI (111)

Silicon is the main raw material for micro- and nanoelectronics. Achievements in these areas are based to a sufficient extent on knowledge of the processes occurring on the surface. Therefore, the study of these processes on a silicon surface is topical today. In this work, the dependences of the angles of water runoff from the silicon surface on the modes of their preparation are experimentally studied. The objects of study were Si single-crystal silicon wafers with (111) surface orientation. An aqueous solution of hydrofluoric acid was used to clean the surface from contamination and natural oxide. To assess the efficiency of cleaning and the state of the studied solid surfaces, the dynamic wetting angle was measured. Distilled water was used as a wetting liquid. It has been found that plates for which ethanol is used in the preparation procedure are better wetted with water. The obtained experimental data are confirmed by the Auger analysis — the plates treated with ethanol contain a smaller amount of carbon-containing impurities. The obtained surface topograms also indicate the effect of surface chemical treatment on its roughness.

THE ROLE OF ELASTIC STRESS DURING THERMOMIGRATION OF LIQUID ZONES BASED ON ALUMINUM IN SILICON

The method of thermomigration of liquid zones based on aluminum makes it possible to create complex structures of closed channels with boundaries formed from p-n junctions in single-crystal silicon wafers. The channels are characterized by the uniformity of their properties, and the pn junctions are characterized by their sharpness. Such structures are used in high-current electronics, photovoltaics, and microelectromechanical converters. Volumetric deformation inside and outside the channel due to alloying of silicon with aluminum leads to the formation of mechanical stresses. The equilibrium shape of the channels formed at high temperatures is determined by the minimum elastic energy and depends on the material parameters and geometry of the structure. Within the framework of the linear theory of elasticity, the behavior of elastic energy during the formation of the structure of thermomigration channels at high temperatures doped with aluminum in a single-crystalline (001) cut disk was studied. The simulation was performed using the finite element method in the COMSOL Multiphysics mathematical package. The study was carried out for practically important structures in which the direction of the edges is oriented along the diagonal of the square. Only such structures do not have breaks during the process of thermomigration. Based on the calculation results, it was revealed that the minimum elastic energy corresponds to structures with different crystalline orientations inside the channel and outside it – in the main silicon matrix. The direction of the crystalline axes inside the channel, corresponding to the minimum elastic energy, is rotated by 45 degrees in the plane of the disk relative to the direction of the axes of the main matrix of the silicon crystal. In addition, calculations showed that with such a turn, the shape of the channels changes. The minimum elastic energy corresponds not to vertical structures, but to inclined ones. The angle of inclination of the pyramids depends on the width of the channels and the distance between them.

Effect of Zn Transition Layer on Properties of Vacuum Deposited Zn-Mg Coating

Zinc coatings have been served as a barrier and a galvanic protection for steel products for over a century. However, with the depletion of zinc resources, it becomes an urgent issue to obtain a new type of zinc coating that uses less zinc and has higher corrosion resistance. In order to develop Zn/ZnMg coatings with better corrosion resistance than traditional galvanized steel and suitable for advanced high strength steel, the vacuum thermal evaporation technique was used to simultaneously deposit Zn/ZnMg coating onto interstitial free steel plates and single-crystal silicon wafers in a high vacuum environment. The microstructure, morphology, adhesion and corrosion resistance behavior of the Zn/ZnMg coating were studied by scratch test, salt spray test and electrochemical method. The results shows that the grain size in the Zn/ZnMg coating tended to increase with the increase of the substrate temperature. After deposited the pure Zn transition layer, the adhesion of the coating has been obviously improved. When the substrate temperature was increased to 200°C, the obtained coating exhibited strong corrosion resistance.

Wafer-scale synthesis of a morphologically controllable silicon ordered array as a platform and its SERS performance.

In this study, we fabricated four different structures using single crystal silicon wafers for surface-enhanced Raman spectroscopy (SERS) applications. For single crystal silicon, different crystal orientations exhibit different physical and chemical properties. In chemical etching, the etching speed of different crystal planes also exhibits significant differences. We first used reactive ion etching (RIE) to process the surface of the substrate, and subsequently used KOH anisotropic wet etching technology to modify the surface of silicon wafers with different crystal orientations and produced four different results. In the RIE stage in an O2 atmosphere, the (110) silicon wafer formed a hexagonal hole structure, and the (100) silicon wafer formed an inverted pyramid hole structure; however, in the RIE-treated substrates in O2 and SF6 atmosphere, the (110) silicon wafer formed a pyramid with a diamond-shaped base, and the (100) silicon wafer showed a columnar structure with a "straw hat" at the top. The formation mechanisms of these four structures were elucidated. We also performed structure-related SERS characterizations of the four different structures and compared their performance differences.

HR-EBSD analysis of in situ stable crack growth at the micron scale

Understanding the local fracture resistance of microstructural features, such as brittle inclusions, coatings, and interfaces, at the microscale is critical for microstructure-informed design of materials. In this study, a novel approach has been formulated to decompose the J-integral evaluation of the elastic energy release rate to the three-dimensional stress intensity factors directly from experimental measurements of the elastic deformation gradient tensors of the crack field by in situ high (angular) resolution electron backscatter diffraction (HR-EBSD). An exemplar study is presented of a quasi-static crack, inclined to the observed surface, propagating on low index {hkl} planes in a (001) single crystal silicon wafer.

Study of the humidity-controlled CeO2 fixed-abrasive chemical mechanical polishing of a single crystal silicon wafer

To address the problem of low polishing efficiency in traditional loose-abrasive chemical mechanical polishing, a humidity-controlled fixed-abrasive chemical mechanical polishing method is proposed, which uses a CeO2 pellet to perform polishing at a specific humidity level. The results of both the nano-scratch tests and the fixed-abrasive polishing experiments demonstrate that the water molecules have an irreplaceable role in the material removal of silicon and that a higher ambient humidity results in better material removal. Fixed-abrasive polishing experiments under saturated humidity can yield a surface roughness less than Ra 2 nm at an efficiency of 0.9 µm/h, and the minimum stress on the polished surface is only a few tens of megapascals. The method is validated to be effective for the stress relief process after grinding.

Millimeter-Wave Permittivity Variations of an HR Silicon Substrate from the Photoconductive Effect.

The photoinduced microwave complex permittivity of a highly resistive single-crystal silicon wafer was extracted from a bistatic free-space characterization test bench operating in the 26.5–40 GHz frequency band under CW optical illumination at wavelengths of 806 and 971 nm. Significant variations in the real and imaginary parts of the substrate’s permittivity induced by direct photoconductivity are reported, with an optical power density dependence, in agreement with the theoretical predictions. These experimental results open the route to ultrafast system reconfiguration of microwave devices in integrated technology by an external EMI-protected and contactless control with unprecedented performance.