Uneven Etching Research Articles

Silicon surface texturing via TBAB-SDS composite additives enhanced copper-assisted chemical etching

Uneven etching and low fabrication efficiency impede the large-scale applications of copper-assisted chemical etching (Cu-ACE) for texturing light-trapping structures on the surface of silicon wafers. To address this, a composite additive composed of tetrabutylammonium bromide (TBAB) and sodium dodecyl sulfate (SDS) was introduced into the Cu-ACE system. The results indicated that TBAB accelerated the etching rate and improved the texturing uniformity, while SDS enlarged the size of the formed structures and enhanced their ultraviolet light absorption efficiency. The prepared inverted pyramid structure reduced the reflectivity of the silicon wafer surface to 3.8 %, thus exhibiting efficient light-trapping capabilities. The etching evolution under various TBAB concentrations and different HF/H2O2 ratios was studied by characterizing the surface contact angle and copper deposition morphology. The results indicated that electrostatic attraction between TBAB and dangling bonds on the silicon wafer surface enhanced material transfer at the reaction interface and changed the electron distribution around dangling bonds, thus facilitating the catalytic metal attack on these bonds. The copper ion reactivity was decreased due to complexation between the dissociated alkyl sulfate ions of SDS and copper ions, which favored the deposition of larger copper nanoparticles during etching, thereby increasing the size of structures. This research offers valuable insights to enable the large-scale applications of Cu-ACE.

Silver-Organic Complex in Photosensitive Silver Pastes for Enhanced Resolution and Aspect Ratio.

Traditional screen printing is an easy approach commonly used for conductive pattern fabrication of electronics but lacks high resolution. Photolithography offers better resolution but is complex. Photosensitive silver pastes (PSP) combine the benefits of both but suffer from undercut issues, causing uneven etching, decreased interfacial adhesion, and thus poor resolutions. In this study, we explore the use of molecular precursors (i.e., silver oxalate) to replace metallic silver particles and enhance the depth of light penetration. Our findings demonstrate a successful solution to the undercut issue, achieving an undercut index of 1.0, indicating an undercut-free scenario and enabling higher resolutions in line and pattern formation. Additionally, our research confirms the feasibility of multilayer stacking of photosensitive pastes, achieving unprecedented aspect ratios in line patterns. By replacing 25% of micrometer silver powder with silver oxalate (PSP-25), we achieved optimal line widths as fine as 10 μm. The three-layer stack of PSP-25 reached a substantial aspect ratio with a height of 29.4 μm and an optimal fringe pattern resolution of 10 μm line width with a 15 μm aisle width. Utilization of silver oxalate was observed to slightly expand the line width, likely due to light scattering by the fine silver nanoparticles (∼40 nm) formed during the photodecomposition of silver oxalate.

Особливості електронно-променевого зварювання магістральних трубопроводів з титанового сплаву

Titanium alloys have high strength and satisfactory weldability. They are widely used in the production of aircrafts and other structural elements in the modern aerospace industry. However, due to a high requirement for aviation and rocket-space technology, increasing the reliability and durability of responsible purpose remains an urgent issue. In this study, the results of welding tubular billets with an electron beam are presented. The subject of this article is the features of tubular billets made of complex titanium alloy electron beam welding. The purpose of this work is to ensure that welds of tubular work pieces have a high level of mechanical properties, based on the welding modes experimental testing results. To achieve this goal, the following tasks were set up and solved in this work: to investigate the mechanism of pore formation in welded joints; to study the effect of electron beam welding on the properties of the weld; ensure high indicators of physical and welded joints mechanical properties. The following research results were obtained. It was possible to obtain satisfactory characteristics of the welded joint by welding in the lower position on the substrate and in the horizontal position. The use of heat treatment increases the strength of welded joints to the level of the base metal. Welded seams, regardless of the welding method, have a coarse-grained structure with liquefaction heterogeneity, which is manifested in uneven etching of the seam. Conclusions: Various metallurgical aspects of titanium electron beam welding were studied. During electron beam welding of tubular blanks, pores are formed mainly near the fusion zone and in the seam axis. Edge mechanical processing, speed reduction, work piece rotation, and welded metal remelting dramatically reduce the number of pores in seams welded in the lower position. Crater removal with a stationary work piece avoids root defect formation in the area of annular seam closure. The obtained results have scientific and practical value in the welded joints of tubular blanks mechanical properties improvement.

Effects of etchant stirring on the surface quality of the metallography sample

Despite its predominantly empirical nature, metallographic etching remains an important sample preparation method that enables microstructural characterization. The poor repeatability is due to the ignorance of etching mechanisms and the human factor, which is mainly associated with the conventional approach. This approach is most commonly practiced by manual immersion of the sample in the etchant. The solution should be gently stirred so that reaction products do not settle on the surface and uneven etching does not occur. Often, stirring is provided by the sample itself or by a magnetic bar. In terms of spatial orientation, etching with the polished surface facing upwards allows the surface to be observed during the process. Some authors recommend etching with the polished surface downwards to minimize the deposition of reaction products. In some cases, a vertical orientation of the sample is recommended to reduce pitting. In this paper, the effect of the etchant stirring method on the surface quality of a metallographic structural steel specimen will be presented. In addition to different etchant stirring methods, different spatial orientations of the sample will also be investigated. To ensure better repeatability and accurate etching time, the samples will be etched using our automated apparatus. The resulting surface of the samples will be analysed using light optical microscopy (LOM) and confocal laser scanning microscopy (CLSM). The development of more reproducible etching methods is essential to obtain accurate microstructure information without artifacts and for advanced quantitative image analysis using deep learning.

Problems of Masking and Anti-Reflective SiO2 in Silicon Technology

The article examines the problems of thermal oxidation of silicon. Oxidation plays an important role in planar technology, which in turn is the basis of the technology of silicon integrated circuits, photodetectors and other solid-state electronics. During our production of silicon p-i-n photodiodes, a number of systematic types of defects and deterioration of product parameters caused by the degradation of masking or anti-reflective coatings during the manufacturing process were observed. A decrease in the insulation resistance of responsive elements in multi-element photodiodes was observed, which contributed to the increase of dark currents. A decrease in the responsivity of the products due to the degradation of the thickness or structure of the anti-reflective coating during technological operations, etc., was also revealed. It was established that the reason for the decrease in insulation resistance is the formation of inversion layers at the Si-SiO2 interface, the presence of which can be detected when measuring CV-characteristics. It was also established that chemical treatment of substrates with SiO2 in boiling acid solutions helps to reduce the thickness of the oxide. To avoid deviation of the thickness of the film from the condition of minimum reflection, it is necessary to grow a thicker layer of anti-reflective coating. It is noted that when etching the oxide during photolithography or when removing the PSG/BSG in hydrofluoric acid, it is not permissible to remove the cassette with plates from the solution for a long time, as this leads to uneven etching of the film due to the flow of the herb on the surface of the substrate. The causes of defect formation in Si and SiO2 during oxidation are given. Thus, with improper mechanical and chemical processing of the plates, cristobalite inclusions may form in the film during oxidation. Cristobalite has a higher density than quartz glass, and the boundaries between amorphous regions and denser crystalline regions represent voids, which can be filled both by impurities from the surface and by the diffusant in the diffusion process. Also, during oxidation in silicon, packing defects are often formed. Centers of defect genesis can be mechanical damage to the plate surface or growth defects.

A novel approach for 3D reconstruction of mice full-grown oocytes by time-of-flight secondary ion mass spectrometry.

Currently two techniques exist for 3D reconstruction of biological samples by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The first, based on microtomy and combining of successive section images, is successfully applied for tissues, while the second, based on sputter depth profiling, is widely used for cells. In the present work, we report the first successful adaptation of sectioning technique for ToF-SIMS 3D imaging of a single cell-fully grown mouse germinal vesicle (GV) oocyte. In addition, microtomy was combined with sputter depth profiling of individual flat sections for three-dimensional reconstruction of intracellular organelles. GV oocyte sectioning allowed us to obtain molecule-specific 3D maps free from artifacts associated with surface topography and uneven etching depth. Sputter depth profiling of individual flat slices revealed fine structure of specific organelles inside the oocyte. Different oocyte organelles (cytoplasm, germinal vesicle, membranes, cumulus cells) were presented on the ion images. Atypical nucleoli referred to as "nucleolus-like body" (NLB) was detected inside the germinal vesicle in PO3- and CN- ions generated by nucleic acids and proteins respectively. Significant difference in PO3- intensity in the NLB central area and NLB border was found. This difference appears as a bright halo around the center area. The NLB size calculated for PO3- and CN- ion images is 12.9 ± 0.2 μm and 11.9 ± 0.2 μm respectively, which suggests that bright halo of PO3- ions is a chromatin compaction on the NLB surface. Areas of approximately 1.0-2.5 μm size inside nucleoplasm with increased PO3- and CN- signal were registered in germinal vesicle. Observed compartments have different sizes and shapes, and they are likely attributed to chromocenters or chromosomes.

Adsorption of acetone and isopropanol on organic acid modified activated carbons

Commercial activated carbon (AC) was modified using formic acid, oxalic acid, and sulfamic acid separately. The effects of the modification on the physicochemical properties of ACs were evaluated using specific surface area and pore distribution, scanning electron microscope, and Fourier transform infrared spectroscopy. After the modification, (i) the BET specific surface area and total pore volume of ACs decreased, (ii) uneven etching trace and white crystal particles were observed on the surface of AC, and (iii) more oxygen-containing functional groups such as OH, CO, CO, and SO were formed on the surface. The effects of the modifications on the adsorption behavior of acetone and isopropanol on ACs at different inlet concentrations were studied from adsorption equilibrium, kinetics, and energy point of view. The results show that the equilibrium adsorption capacity has been greatly improved by the modification of organic acids. The adsorption isotherms of acetone and isopropanol on ACs are well fitted by both Langmuir and Freundlich equations. Characteristic adsorption energy values of acetone and isopropanol slightly increase with increasing of oxygen functional groups on the ACs surface. The adsorption kinetics of acetone and isopropanol on ACs are best described by Bangham kinetics model.

A Novel Pore-Scale Thermal-Fracture-Acidizing Model With Heterogeneous Rock Properties

Summary Fracture acidizing is a well-stimulation technique used to improve the productivity of low-permeability reservoirs and to bypass deep formation damage. The reaction of injected acid with the rock matrix forms etched channels through which oil and gas can then flow upon production. The properties of these etched channels depend on the acid-injection rate, temperature, reaction chemistry, mass-transport properties, and formation mineralogy. As the acid enters the formation, it increases in temperature by heat exchange with the formation and the heat generated by acid reaction with the rock. Thus, the reaction rate, viscosity, and mass transfer of acid inside the fracture also increase. In this study, a new thermal-fracture-acidizing model is presented that uses the lattice Boltzmann method to simulate reactive transport. This method incorporates both accurate hydrodynamics and reaction kinetics at the solid/liquid interface. The temperature update is performed by use of a finite-difference technique. Furthermore, heterogeneity in rock properties (e.g., porosity, permeability, and reaction rate) is included. The result is a model that can accurately simulate realistic fracture geometries and rock properties at the pore scale and that can predict the geometry of the fracture after acidizing. Three thermal-fracture-acidizing simulations are presented here, involving injection of 15 and 28 wt% of hydrochloric acid into a calcite fracture. The results clearly show an increase in the overall fracture dissolution because of the addition of temperature effects (increasing the acid-reaction and mass-transfer rates). It has also been found that by introducing mineral heterogeneity, preferential dissolution leads to the creation of uneven etching across the fracture surfaces, indicating channel formation.

Uniformly thinned optical fibers produced via HF etching with spectral and microscopic verification

A method for producing uniformly thinned (etched) optical fibers is described, which can also be employed to etch optical fibers containing a Bragg grating (FBG) uniformly for evanescent-field-based sensing and other applications. Through a simple modification of this method, the fabrication of phase-shifted FBGs based on uneven etching is also shown. The critical role of how a fiber is secured is shown, and the success of the method is illustrated, by differential interference contrast microscopy images of uniformly etched FBGs. An etched FBG sensor for the monitoring of the refractive index of different glycerin solutions is demonstrated.

Guided Three-Dimensional Catalyst Folding during Metal-Assisted Chemical Etching of Silicon

In recent years metal-assisted chemical etching (MaCE) of silicon, in which etching is confined to a small region surrounding metal catalyst templates, has emerged as a promising low cost alternative to commonly used three-dimensional (3D) fabrication techniques. We report a new methodology for controllable folding of 2D metal catalyst films into 3D structures using MaCE. This method takes advantage of selective patterning of the catalyst layer into regions with mismatched characteristic dimensions, resulting in uneven etching rates along the notched boundary lines that produce hinged 2D templates for 3D folding. We explore the dynamics of the folding process of the hinged templates, demonstrating that the folding action combines rotational and translational motion of the catalyst template, which yields topologically complex 3D nanostructures with intimately integrated metal and silicon features.

A Theoretical Study of Acid-Fracture Conductivity Under Closure Stress

Summary The conductivity of acid-etched fractures depends on spaces along the fracture created by uneven etching of the fracture walls remaining open after fracture closure. In this study, we have modeled the deformation of the irregular fracture surfaces created by acid etching and the resulting fracture conductivity as closure stress is applied to the fracture. In our previous work, we modeled the dissolution of the fracture surfaces in a formation having small-scale heterogeneities in both permeability and mineralogy. This model yielded the geometry of the etched fracture at zero closure stress. Beginning with this profile of fracture width, we have modeled the deformation of the fracture surfaces as closure stress is applied to the fracture. At any cross section along the fracture, we approximate the fracture shape as being a series of elliptical openings. Assuming elastic behavior of the rock, we calculate how many elliptical gaps remain open and their sizes as a function of the applied stress. The sections of the fracture that are closed are assigned a conductivity because of small-scale roughness features using a correlation obtained from laboratory measurements of acid-fracture conductivity as a function of closure stress. The overall conductivity of the fracture is then obtained by numerically modeling the flow through this heterogeneous system. Our previous work shows that high fracture conductivity can be created in acid fracturing if heterogeneity of the rock leads to the formation of channels along the fracture surfaces. In this study, we have determined how the channels in acid fracturing remain open as closure stress is applied. This model predicts the rock characteristics that are necessary for acid-fracture conductivity to be sustainable under high closure stress.

Enhanced scanning ion microprobe image analysis for rough surface samples as an alternative to SIMS depth profiling

AbstractThe usefulness of scanning ion microprobe (SIM) image analysis by a gallium focused ion beam (FIB) on a bevelled sample surface is investigated. To improve the low secondary ionization yields of elements caused by the gallium bombardment, the oxygen ions for the positive ion detection and the caesium ions for the negative ion detection were in‐situ implanted with a dose of 1016–1017 atoms/cm2 prior to imaging analysis. A significant enhancement of ion image sensitivity in the ion‐implanted area compared with that in the non‐implanted area was observed. The enhanced SIM image analysis for the highly magnified bevel is especially useful for multilayered structures with rough surfaces. That is because the secondary ion mass spectrometry (SIMS) depth profiles for the rough surface samples do not give accurate depth information due to the significant distortion and degradation of the profiles caused by uneven etching. This technique can be an alternative to the SIMS depth profiling for rough surface samples. Copyright © 2004 John Wiley & Sons, Ltd.

Acid-Fracturing Treatment: A Surface-Topography Analysis of Acid-Etched Fractures To Determine Residual Conductivity

Summary A fracture-acidizing treatment of carbonate formations can be considered successful when a relatively good fracture conductivity remains after treatment. To reach such a goal, an uneven etching of the fracture by acid is expected, so that channels are created that hydraulically maintain the fracture open, once the pressure is released after the job, and thus enhance productivity. Residual conductivity is the consequence of uneven etching of the surface, but the way this etching occurs in the field is not well understood and, therefore, poorly described. We, thus, propose, in this paper, an experimental methodology to investigate and characterize quantitatively how acid injection conditions affect the fracture surfaces, how the created rough surface is able to support the stress, and, finally, how fracture conductivity can be estimated from the surface topography. The statistical investigation of surface topography associated with acidizing experiments proposed in this paper, provides a new and interesting method for designing an acid fracturing job. It can be used as an aid to select the best fluid formulation and flow rate for a given formation type and well conditions and to forecast the behavior of the fracture after the treatment.

Differences in the nucleation rate of YBa 2Cu 3O 7-δ on patterned (001) LaAlO 3 substrates

The microstructures of laser deposited c-axis oriented YBa 2Cu 3O 7-δ (YBCO) thin films have been characterised by scanning and transmission electron microscopy. Grain boundaries were produced using substrates with wavy step edge profiles on cubic (001) LaAlO 3. The wavy step edge profiles simulated a meandering profile which may arise due to uneven etching of mask and substrate during conventional pattering procedures. The nucleation rate of the a-axis oriented film in the step region varied along the wave profile. The results indicate that a well defined grain boundary geometry and behaviour require a straight step profile on a sub micron scale. In addition, the YBCO nucleation in the step region can be suppressed by choosing a step direction which deviates from the [100] LAO and [010] LAO.

Quantifying the effects of uneven etching during the SIMS analysis of periodic doping structures grown by silicon MBE

AbstractProblems associated with the secondary ion mass spectrometry (SIMS) depth profiling of periodic doping structures are discussed with reference to experiments on a boron‐in‐silicon modulation doping structure and a boron‐antimony silicon super‐lattice, both grown by silicon molecular beam epitaxy (MBE). The effects of uneven etching during SIMS analysis are compared with the effects of dopant diffusion during growth. Uneven etching is modelled with an algorithm in which the macrotopography of the crater base is described in terms of an unevenness function f(x, y). Simulation depth profiles involve passing craters of this topography f(x, y) through specified, laterally homogeneous, doping distributions ρp(z) in a series of equal depth interations. The predicted SIMS signal is proportional to the amount of dopant sputtered per depth iteration. The model explains the peak shapes and the loss of depth resolution with depth that are observed experimentally. The effects of dopant diffusion during growth are found by re‐heating parts of the wafer to the growth temperature for various periods of time and then SIMS depth profiling them (thermal cycling).

Changes in the structure and properties with overheating of Al?Mg alloys

1. Overheating of Al−Mg alloys occurs in two stages. In the early stage micropores are formed in binary alloys, uneven etching decreases, and the boundaries of dendritic cells are revealed in more highly alloyed alloys. In the final stage macropores are observed in binary alloys and melting in more highly alloyed alloys. 2. Heat-treated alloys retain the cast structure. Micropores and macropores are formed in β-phase sites in binary alloys. In more highly alloyed alloys melting occurs in high-etching sections. 3. With overheating the character of the fracture changes from ductile (for quenched alloys) to intercrystalline in the early stage of overheating and mixed (along melted sections) in the later stage of overheating.

Oxygen etching method of making an electron microscopy study of polyethylene terephthalate films

I~ T~E earlier works by Spit and Anderson [1, 2] it was found tha t if ultrafine cuts and dispersed polymers were etched in a gas discharge structural details could be made visible. This is a t t r ibuted to changes in the depth of the specimen due to the uneven etching of the parts of the polymer with different densities. On the photographs of etched sections and fibres, the authors detected supramolecular formations 300-400 A in size, with preferred orientation perpendicular to the fibre axis.