Etching In Acid Solution Research Articles

Investigation of Low-Cost Surface Processing Techniques for Large-Size Multicrystalline Silicon Solar Cells

The subject of the present work is to develop a simple and effective method of enhancing conversion efficiency in large-size solar cells using multicrystalline silicon (mc-Si) wafer. In this work, industrial-type mc-Si solar cells with area of125×125 mm2were acid etched to produce simultaneouslyPOCl3emitters and silicon nitride deposition by plasma-enhanced chemical vapor deposited (PECVD). The study of surface morphology and reflectivity of different mc-Si etched surfaces has also been discussed in this research. Using our optimal acid etching solution ratio, we are able to fabricate mc-Si solar cells of 16.34% conversion efficiency with double layers silicon nitride (Si3N4) coating. From our experiment, we find that depositing double layers silicon nitride coating on mc-Si solar cells can get the optimal performance parameters. Open circuit (Voc) is 616 mV, short circuit current (Jsc) is 34.1 mA/cm2, and minority carrier diffusion length is 474.16 μm. The isotropic texturing and silicon nitride layers coating approach contribute to lowering cost and achieving high efficiency in mass production.

Achieving finer pores and ligaments in nanoporous palladium–nickel thin films

Nanoporous palladium nickel (np-PdNi) was produced by dealloying PdNi alloy thin films. The pore and ligament dimensions were reduced by 50% when surfactants were added to the sulfuric acid etching solution. Changes in film composition and biaxial film stress were used to track the dealloying evolution in the surfactant-modified etching solution. Ultrasonic agitation was also used to enhance dealloying and shortened the required time from 5 h to 1 h, while retaining a pore/ligament size of ∼5 nm.

An Environment-Friendly Surface Pretreatment of ABS Resin Prior to Electroless Plating

An environment-friendly etching system consisting of the H 2 SO 4 ―MnO 2 colloid was used to investigate surface etching for acrylonitrile-butadiene-styrene (ABS) resin as a replacement for conventional chromic acid etching solutions. With the etching treatment, many small cavities appeared on the ABS surface, and the surface average roughness was increased from 40 to 388 nm. The adhesion strength between the ABS surface and the electroless copper film was improved greatly with the etching treatment. The average adhesion strength reached 1.19 kN m ―1 , which is close to that of chromic acid etching treatment (1.42 kN m ―1 ). The Fourier transform infrared spectra and contact angle measurements indicated that ―COOH and -OH groups were formed on the ABS surface with the etching treatment, and the density of the groups on the surface increased with the etching time. The X-ray photoelectron spectroscopy results also demonstrated that C=C bonds on the surface of ABS resin were oxidized to carboxylic acids in the etching process, but the C≡N bonds of acrylonitrile were not oxidized. The H 2 SO 4 ―MnO 2 colloid is an effective and environment-friendly surface etchant for ABS surface etching.

다결정 실리콘 태양전지의 표면 텍스쳐링 및 반사방지막의 영향

The effects of texturing and anti-reflection coating on the reflection properties of multi-crystalline silicon solar cell have been investigated. The chemical solutions of alkaline and acidic etching solutions were used for texturing at the surface of multi-crystalline Si wafer. Experiments were performed with various temperature and time conditions in order to determine the optimized etching condition. Alkaline etching solution was found inadequate to the texturing of multi-crystalline Si due to its high reflectance of about 25%. The reflectance of Si wafer texturing with acidic etching solution showed a very low reflectance about 10%, which was attributed to the formation of homogeneous. Also, deposition of ITO anti-reflection coating reduced the reflectance of multi-crystalline si etched with acidic solution(<TEX>$HF+HNO_3$</TEX>) to 2.6%.

Nanocone array glass

We report a novel method of producing ordered arrays of glass nanocones with precisely controlled height, lattice constant and aspect ratio. As with nanochannel glass, fibre drawing, bundling and redrawing are used to produce structured glass composite material. The surface of the composite is etched to form nanocones through a differential etching process. The lattice constant of the arrays ranges from 40 µm to 1.6 µm, while the aspect ratio of the nanocones is varied from 0.4 to 13 by simple changes in the chemistry of the hydrofluoric acid etching solution.

Alumina nanostructures prepared by two-step anodization process

Alumina nanostructures were obtained by two-step anodization process. The porous anodic aluminum oxide(AAO) membranes were anodized in oxalic acid, which was subsequently treated with chemical etching process with 1.0 mol/L sodium hydroxide solution, or mixed solution of phosphoric acid (6.0%) and chromic acid (1.8%), respectively. Field emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM) were employed to character the morphology and structure of the obtained alumina nanostructure. It is found that alumina nanowires are generated in the acidic chemical etching solution, while nanotube structures are formed in the alkaline solution. The influence of acid and alkaline solution on alumina morphologies in the chemical etching process was discussed.

The Study of Copper Etching in Acid Solution

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Fabrication of new elements and devices on the glass surface under a combined action of short-wavelength radiation and ion-exchange diffusion

The possibilities for using the photocrystallization diffusion method in combination with low temperature ion exchange and etching in acid solutions to fabricate devices of integrated optics and optoelectronics on the surface of alkali aluminosilicate glasses are demonstrated. A two-stage low temperature ion-exchange technique is developed for producing surface crystallized layers with a controlled thickness and configuration. These layers can serve as a photomask on the glass surface in the course of high-temperature ion exchange. Etching of the glasses and crystals on their base in solutions of mineral acids is investigated. A procedure is proposed for preparing the relief structures on the glass surface.

CVD Diamond Coated Cemented Carbide Inserts

The cutting performance of CVD diamond coated cemented carbide (WC-6%Co) inserts pretreated by etching was studied and compared with those of uncoated cemented carbide inserts. Diamond coated inserts pretreated with acid etching and Murakami solution etching yielded a cutting lifetime of 136 and 180 min , respectively, for cutting an aluminium alloy of Al-12%Si with a cutting speed v of 201 m/min, a feed rate f of 24 mm/min and a cutting depth ap of 0·5 mm. Uncoated inserts yielded a lifetime of only 15 min. This demonstrates that the application of CVD diamond coating to WC - 6%Co inserts can greatly improve their cutting performance and increase their cutting lifetime.

Fabrication and application of high quality diamond-coated tools

Diamond-coated tools were fabricated using Co cemented carbide inserts as substrates by electronically aided hot filament chemical vapor deposition (EACVD). An amount of additive in an acid solution was used to promote the Co etching of the substrate surface. The surface of the WC–Co substrate was decarburized by microwave plasma with Ar–H 2 gas. The effect of the new substrate pre-treatment on the adhesion of the diamond films was investigated. A boron-doped solution was brushed on to the tool surface to diffuse the boron into the substrate during diamond deposition. A new process was used to reduce the surface roughness of the diamond thin films by appropriately controlling the deposition parameters, which consists of a composite diamond film chemical vapor deposition procedure including first the deposition of rough polycrystalline diamond and then fine-grained diamond. The research results show that the pre-treatment, including both Co etching in acid solution and Ar–H 2 etching decarburization by microwave plasma, is an effective method to enhance the adhesive strength. An adequate amount of boron dopant solution can effectively suppress cobalt diffusion to the surface and avoid the catalytic effect of Co at high temperature. The composite film CVD process can deposit smooth diamond films with low surface roughness. It is of great significance for the improvement of the cutting performance of diamond-coated tools to use the above new technology to deposit diamond coatings with low surface roughness and high adhesive strength on WC–Co substrates.

On the nature of hydrogen-related centers in p-type irradiated silicon

Hydrogen interaction with the radiation defects is studied by the DLTS and MCTS techniques. Hydrogenation was carried out during wet chemical etching in acid solutions and following reverse bias annealing at 380 K. The levels H4= E v+0.28 eV and E4= E c–0.31 eV are formed as a result of the hydrogenation in all samples irradiated with electrons at room temperature. The levels are not found in irradiated samples which were annealed at 620–650 K before the hydrogenation. Another prominent level H3= E v+0.51 eV is introduced by hydrogenation of as-irradiated float-zone silicon. Czochralski samples have to be annealed at 450 K before hydrogenation to form the H3 level. The H3 center is not formed in the samples annealed at ∼650 K before hydrogenation. The nature of the hydrogen-related centers is discussed.

New approach to isotropic texturing techniques on multicrystalline silicon wafers

Multicrystalline silicon wafers were isotropically textured using two kinds of modified acid texturing methods. One of the modifications is based on the introduction of the spray deposition method into the conventional acid etching of Si wafers. Silicon dioxide or photo-resist was sprayed on the Si wafers and used as masks for following acid etching process. The acid etching solution was modified with \( H_2 SO_4 \) and various additives. Short circuit densities of the solar cells fabricated using those modified acid texturing were measured to be in the range between 30.8 and \( 31.4mA/cm^2 \), which were at least \( 1.6mA/cm^2 \) higher than those from alkaline textured solar cells.

Hydrogen interaction with defects in electron-irradiated silicon

Hydrogen-induced passivation and modification of radiation defect electrical activity in silicon are studied by deep-level transient spectroscopy. Hydrogen is incorporated into high-energy electron-irradiated crystals during chemical etching in acid solution at room temperature, followed by reverse-bias annealing of p-type samples at 380K. It is observed that the concentrations of major radiation defects (divacancies, A- and K-centers) are reduced in the hydrogen-rich regions, while a number of novel hydrogen-related deep-level centers appear. The complexes with the energy level at Eν+0.28eV are formed due to hydrogenation of the K-centers.

Determination of fluorochemical surfactants in acid etch baths by ion chromatography with on-line matrix elimination

Fluorochemical surfactants are added to acid etching solutions to ensure good wetting of the wafer surface. Methods were developed to determine the fluorochemical surfactant FC-93 in an etch bath composed of HF–ammonium fluoride (1:6) and the fluorochemical surfactant FC-95 in an etch bath containing concentrated HF, HCl and HNO 3. On-line matrix elimination was accomplished on a polymeric reversed-phase column followed by separation on a multiphase HPLC column, and detection by suppressed conductivity. Using this method, we determined 5 mg/l of the surfactant FC-93 in 100 μl of the etch bath.

In-Situ Chemical Concentration Control for Wafer Wet Cleaning

This paper demonstrates the use of conductivity sensors to monitor and control the concentration of RCA cleaning and hydrofluoric acid (HF) etching solutions. Commercially available electrodeless conductivity sensors were used to monitor and control the concentration of these process solutions. A linear relationship between the conductivity of the solution and the chemical concentration was obtained within the range studied. A chemical injection scheme was developed to maintain the chemical concentration within specified limits. Different concentrations of RCA-based cleaning solutions and HF solutions were investigated. Results show that these techniques are suitable for monitoring and controlling the concentration of chemicals in the process tanks for better process control. These techniques provide low cost of ownership of the process by using dilute chemicals and longer bath life (i.e., a more environmentally sound process).

Transformation of deep-level spectrum of irradiated silicon due to hydrogenation under wet chemical etching

The effect of wet chemical etching in acid solutions on the energy spectrum of n- and p-type silicon crystals previously irradiated with high-energy electrons is studied by deep-level transient spectroscopy. It is observed that together with the well known radiation defects a number of novel deep-level centres appear near the etched surface. The depth profiles of the deep-level centres are investigated depending on the irradiation dose and the temperature of subsequent annealing. The novel centres observed are shown to be complexes of radiation defects with the hydrogen atoms which penetrated into the crystal during etching. The origin of some of these centres from the particular vacancy-related defects is established. A simple quantitative description is given of hydrogen atom penetration during the etching and formation of the hydrogen - radiation defect complexes. Based on this analysis, the radius of hydrogen capture to the well known A-centre (vacancy - oxygen complex) is estimated and the centre with an energy level of eV is identified as a complex of the A-centre with two hydrogen atoms.

Membrane based system for ultrapure hydrofluoric acid etching solutions

The use of membranes to reprocess thousands of tons of hydrofluoric acid (HF) etching solutions per year is different from all previous applications of reverse osmosis (RO) and opens new opportunities for membrane based technologies. This novel application is based on both water and hydrofluoric acid permeating the RO membrane while all other impurities are rejected by it. For the first time, a spiral wound module was used here to process feeds representative of the complex multicomponent hydrofluoric acid etching solutions found in a wafer fabrication laboratory. Our new results were obtained with spiral wound membrane modules to determine the rejection and permeation of the various components along with the fluxes obtainable in realistic systems. HF was found to permeate almost 100% through the membranes while over 90% of the fluosilicic acid (the major impurity) is rejected, in a single pass. The higher the concentration of fluosilicic acid in the range of interest the better the rejection of it. Detailed analysis of the trace elements present in such HF etching solutions, which are responsible for “killer” defects in semiconductor device manufacturing, show over 99% removal of these elements in a single pass by the membranes. The economic analysis of the process indicates that reverse osmosis is attractive for the treatment of spent HF etching solutions. The performance of such spiral wound membrane systems, which represent closely the behavior of actual industrial HF reprocessors, is shown here to have tremendous potential both for reprocessing the etching solutions waste and may be feasible for ultrapurifying VLSI and ULSI grade virgin hydrofluoric acid.

Epitaxial lift-off of thin InAs layers

We describe the use of the epitaxial lift-off technique to remove thin layers of InAs from the GaAs substrates on which they were grown and subsequently bonded to glass and silicon substrates. Lift-off was accomplished by taking advantage of the high etching selectivity between AlSb and InAs in an aqueous hydrofluoric acid etching solution, allowing a thin layer of AlSb to serve a sacrificial layer to facilitate the lift-off of the InAs. The InAs layers were transferred with little measurable effect on the electrical and structural properties of the films, as evidenced by Hall effect and x-ray measurements. The technique can easily be extended to transfer more-complex GaSb/AlSb/InAs structures.

Corrosion of aluminium nitride substrates in acid, alkaline solutions and water

Aluminium nitride substrates were immersed in acid, basic solutions and deionized water for 1–120 h at room temperature. The corrosion rates are higher in basic solutions (NaOH and KOH) than those in acid solutions (CH3COOH, HCOOH, HNO3, HCl and H2SO4) and deionized water. The weight loss of AIN corroded in alkali aqueous reaches 70% and results in an increase in surface roughness ranging from 10 nm to 7 μm after 3 days corrosion. However, the weight loss in acid solution is only 1/700 of the alkali case. Violent chemical reactions between AIN and basic solutions were observed. Na2O, or Na2Al2O4·6H2O, is the intermediate product, and NaOH is a catalytic agent of the reaction. The surface morphology of the AIN etched by alkaline solutions is coral-like in microscopic view and appears like hills. In contrast, only several atomic layers of AIN surface are etched off in acid solutions and in deionized water. The lightly etched surface is mirror-like and flat, and the shapes of the grains are visible under the microscope, as the corrosion rate of each AIN grain varies with different crystal orientations. Consequently, after etching in acid solutions, the resulting microscopic surface morphology looks like a map of a jigsaw puzzle.

Photopatterning of Self-Assembled Alkanethiolate Monolayers on Gold: A Simple Monolayer Photoresist Utilizing Aqueous Chemistry

In this paper we demonstrate that self-assembled monolayers (SAMs) of alkanethiols on gold can be used as effective photoresists. UV photolysis of an alkanethiol SAM generates the corresponding sulfonate in the monolayer film. The sulfonate is easily rinsed off of the surface with water, exposing a clean gold substrate, which can then be modified with subsequent chemistry. We describe here experiments in which an alkanethiol SAM on a gold film on silicon is irradiated through a mask, followed by immersion of the sample in an aqueous acid etching solution (HCI:HNO[sub 3]:H[sub 2]O = 3:1:4). The gold is etched away from the areas which have been exposed to UV radiation leaving a pattern which reproduces the original mask. The spatial resolution in the present experiments is limited by the mask which is a 6-[mu]m wire grid. Scanning electron microscopy images of patterned samples show sharp edges to the features suggesting that spatial patterning on the 1-[mu]m scale should be attainable with this simple chemistry. 11 refs., 4 figs.