• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.38-43
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• 2019

Electrochemical etching is a popular process to apply metal patterning in various industries. In this study, the electrochemical etching using a patterned copper layer was proposed to fabricate multilayered structures. The process consists of electrodeposition, laser patterning, and electrochemical etching, and a repetition of this process enables the production of multilayered structures. In the fabrication of a multilayered structure, an etch factor that reflects the etched depth and pattern size should be considered. Hence, the etch factor in the electrochemical etching process using the copper layer was calculated. After the repetition process of electrochemical etching using copper layers, the surface characteristics of the workpiece were analyzed by EDS analysis and surface profilometer. As a result, multilayered structures with various shapes were successfully fabricated via electrochemical etching using copper layers.

• Journal of Institute of Convergence Technology
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• v.2 no.2
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• pp.25-29
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• 2012

Micro machining technologies have been required to satisfy various conditions in a high-technology industry. Micro electrochemical process is one of the most precision machining methods. Micro electrochemical process has been divided into electrochemical etching through protective layer and electrochemical machining using ultrashort voltage pulses. Micro shaft can be fabricated by electrochemical etching. The various protective layers such as photo-resist, oxide layer and oxidized recast layer have been used to protect metal surface during electrochemical etching. Micro patterning on metal surface can be machined by electrochemical etching through protective layer. Micro hole, groove and structures can be easily machined by electrochemical machining using ultrashort voltage pulses. Recently, the groove with subnanometer was machined using AFM.

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.330-335
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• 2020

Silicon surface nanostructures, which can be easily prepared by electrochemical etching, have attracted considerable attention because of its useful physical properties that facilitate application in diverse fields. In this work, electrochemical and electrochemical-scanning tunneling microscopic (EC-STM) techniques were employed to study the evolution of surface morphology during the electrochemical etching of Si(111)-H in a fluoride solution. The results exhibited that silicon oxide of the Si(111) surface was entirely stripped and then the surface became hydrogen terminated, atomically flat, and anisotropic in the fluoride solution during chemical etching. At the potential more negative than the flat band one, the surface had a tendency to be eroded very slowly, whereas the steps of the terrace were not only etched quickly but the triangular pits also deepened on anodic potentials. These results provided information on the conditions required for the preparation of porous nanostructures on the Si(111) surface, which may be applicable for sensor (or device) preparation (Nanotechnology and Functional Materials for Engineers, Elsevier 2017, pp. 67-91).

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.398-400
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• 1998

In this paper, the etching studies for n-GaN were carried out using the wet chemical, the photo-enhanced-chemical, and the electro-chemical etching methods. The experimental results show that n-GaN is etched in diluted NaOH solution at room temperture and the etched thickness of NaOH and electron concentrations. Te etching rate of n-GaN samples with n.simeq.1*10$^{19}$ cm$^{-3}$ were used to compare the photo-enhanced-chemical etching with the electrochemical etching methods. The removed thickness was 680.angs./25min by the electrochemical etching methods. The removed thickness was 680 .angs./25min by the electrochemical etching method ad 784.angs./25min by the photoenhanced-chemical etching method. The patterns are 100.mu.m*100.mu.m rectangulars covered with SiO$_{2}$film. It is shown that the profile of etched side-wall of the pattern is vertical without dependance of the n-GaN orientations.

• Journal of the Korean Electrochemical Society
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• v.14 no.4
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• pp.191-195
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• 2011

Wet chemical etching methods were utilized to conduct Si surface texturing, which could enhance photoelectrochemical hydrogen generation rate. Two different etching methods tested, which were anisotropic metal-catalyzed electroless etching and isotropic etching. The Si nano-texture that was fabricated by the anisotropic etching showed ~25% increase in photocurrent for H2 generation. The photocurrent enhancement was attributed to the reduced reflection loss at the nano-textured Si surface, which provided a layer of intermediate density between water and the Si substrate.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.109-112
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• 2002

The structural and optical features of Porous Silicon(PS) were investigated; the porous silicon was prepared by electrochemical etching of silicon wafers in HF solution. The morphologies and Photoluminescece(PL) features of the PS were investigated in terms of etching time, current density and aging conditions. The average pore diameter and pore depth were determined by current density and etching time, respectively. As-prepared PS exhibited the maximum PL peak at the wavelength of ∼ 450 nm. The degree of deviation from as-prepared PS during aging treatment seemed to depend on the microstructure as well as morphology of the PS. It is found that etching current density played an important role on the microstructural features of the PS.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.23-27
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• 2011

Fabrication of porous silicon(PS) double layer by electrochemical etching is the first step in process of ultrathin solar cell using PS layer transfer process. The porosity of the porous silicon layer can be controlled by regulating the formation parameters such as current density and HF concentration. PS layer is fabricated by electrochemical etching in a chemical mixture of HF and ethanol. For electrochemical etching, highly boron doped (100) oriented monocrystalline Si substrates was used. Ths resistivity of silicon is $0.01-0.02\;{\Omega}{\cdot}cm$. The solution composition for electrochemical etching was HF (40%) : $C_2H_5OH$(99 %) : $H_2O$ = 1 : 1 : 2 (by volume). In order to fabricate porous silicon double layer, current density was switched. By switching current density from low to high level, a high-porosity layer was fabricated beneath a low-porosity layer. Etching time affects only the depth of porous silicon layer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.7
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• pp.616-621
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• 2009

Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating(ARC) and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si ARC layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layers were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The structure of porous Si layers was investigated with SEM. The formation of a nanoporous Si layer about 100nm thick on the textured silicon wafer result in a reflectance lower than 5% in the wavelength region from 500 to 900nm. Such a surface modification allows improving the Si solar cell characteristics. An efficiency of 13.4% is achieved on a monocrystalline silicon solar cell using the electrochemical technique.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.482-488
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• 2012

To fabricate a precise micro metal mold, the electrochemical etching process has been researched. We investigated the electrochemical etching process numerically and experimentally to determine the etching tendency of the process, focusing on the current density, which is a major parameter of the process. The finite element method, a kind of numerical analysis, was used to determine the current density distribution on the workpiece. Stainless steel(SS304) substrate with various sized square and circular array patterns as an anode and copper(Cu) plate as a cathode were used for the electrochemical experiments. A mixture of $H_2SO_4$, $H_3PO_4$, and DIW was used as an electrolyte. In this paper, comparison of the results from the experiment and the numerical simulation is presented, including the current density distribution and line profile from the simulation, and the etching profile and surface morphology from the experiment. Etching profile and surface morphology were characterized using a 3D-profiler and FE-SEM measurement. From a comparison of the data, it was confirmed that the current density distribution and the line profile of the simulation were similar to the surface morphology and the etching profile of the experiment, respectively. The current density is more concentrated at the vertex of the square pattern and circumference of the circular pattern. And, the depth of the etched area is proportional to the current density.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.257-265
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• 2021

In this study, we report niobium (Nb) with hierarchical porous structure produced by a one-pot, HF-free electrochemical etching process. It is proved experimentally that a well-defined hierarchical porous structure is produced from the combination of a limited repetition of pulse etching and high concentration of aggressive anion (i.e., SO₄^2-), which results in hierarchical pores with high order over 3. A formula is derived for the surface area of porous Nb as a function of the hierarchical order of pores while the experimental surface area is estimated on the basis of the electrochemical gas evolution rate on porous Nb. From the comparison of the theoretical and experimental surface areas, an in-depth understanding was gained about porous structure produced in this work in terms of the actual pore shape and hierarchical pore order.