Papers by Keyword: Etching

Abstract: Plasma chemical vaporization machining (PCVM) is a high-rate etching method that uses atmospheric-pressure plasma. Its application to the plasma dicing of SiC wafers is anticipated. However, since the reaction is mainly driven by neutral radicals, it is difficult to maintain anisotropy, and issues such as side etching are of concern. In this study, PCVM processing was performed using SF₆ gas with a Ni mask to investigate vertical and lateral etching behaviors. We achieved vertical etching of 100 µm within approximately 35 minutes, and lateral side etching of about 50 µm. The lateral etch rate remained nearly constant, whereas the vertical etch rate was initially high but decreased as the etching progressed, approaching the lateral rate. Finite element-based electrostatic field analysis revealed that, as the etching depth increased, electric field shielding by the mask weakened the field at the bottom of the trench, leading to a transition toward neutral radical-dominated reactions.

Abstract: An innovative method of obtaining thin films of semiconductors and other materials, which is based on the differences in components solubility, density, and atomic mass, is developed. Process of producing a thin film of a substance A starts by choosing of another component – substance B that may form a two-component A–B solid solution. Then, it has to be selected third component – substance C that must dissolve substance B well, but A does not. The selection of the composition and conditions of application of the chemical etching process ensure the removal of C and B dissolved in it from the surface of A. The method provides both low- and high-temperature processes. The proposed new principle of obtaining thin films would be attractive due to their reduced size, tunable properties, proper adhesion, preservation of high reliability, possibility of further miniaturization in electronics, and cost reduction.

Abstract: This presentation focuses on semiconductor wafer cleaning technology, one of the most critical technologies in semiconductor device manufacturing for obtaining high yield and reliability, and discusses the past, present, and future of the technology. Emphasis is placed on the review of contamination control and cleaning technologies in the early days since the invention of the transistor. To celebrate the 30+1-year anniversary of the UCPSS, a review will be given of both the first conference held in Leuven in 1992 and the second one held in Bruges in 1994. There will be more research challenges and business opportunities in environmentally benign, innovative damage-free wafer cleaning and surface preparation technologies for future applications.

Abstract: Nanostructuring of the surface occurs after annealing at high temperature of 4H-SiC samples. The surface morphology becomes needle-shaped like black silicon. The roughness of the surface also increases due to annealing and a slight etching of nanostructured zones occurs with an accentuated phenomenon at the boundaries. Electroluminescence is obtained by applied forward bias on fabricated PIN diode structures with localized nanostructurated windows in surface. Light intensity seems to be more sensitive to the initial orientation of the substrate and less to the annealing temperature in the 1500°C-1700°C range.

Abstract: In this project, the surface structure of III-V semiconductor, GaAs, was altered to enhance the optical and electronic properties of the semiconductor. This project involved the designing and fabrication of non-porous and porous GaAs structures using SILVACO TCAD tools. The porous GaAs with different pore depth were designed and simulated to investigate the effect of pore depth on the optical and electrical properties of GaAs semiconductor. The pore depth of porous GaAs structure was varied with 2, 4, 6 and 8 μm. The porous GaAs structures were then tested for the metal-semiconductor-metal (MSM) photodetector device application. The non-porous and porous GaAs MSM photodetectors were compared systematically through current-voltage (I-V) characteristics, current gain, and spectral response. The result showed that the porous GaAs MSM photodetector has better performance in terms of electrical and optical properties than the non-porous photodetector. Amongst the MSM GaAs photodetectors, the porous GaAs photodetector with pore depth of 6 μm obtained the highest current gain value of 3.22. While for optical properties, the spectral response showed the current intensity of 11.370 µA which was recorded at the peak wavelength of 880 nm. Therefore, porous GaAs showed good potential and can be used for optoelectronic device applications such as MSM photodetector.

Abstract: During cavitation investigations with manganese-aluminum-bronzes (MAB) in seawater using ultrasound (US), it was found that the microstructure of the bronze was developed by etching. To investigate this phenomenon in more detail, metallographically polished MAB samples were US-treated in synthetic seawater. On the one hand, pulsed ultrasound was used with a sonotrode in order to be able to observe the effects of cavitation. On the other hand, an ultrasonic bath with less power than the sonotrode was used to investigate the influence of ultrasound on the electrochemical response of the MAB. It was found that the k-phase is attacked most severely by cavitation, followed by β-phase and the α-phase. Potentiostatic measurements indicated that the transport of oxygen to, and of metal ions from the metal surface is enhanced by the ultrasound, which then leads to increased corrosion rates.

Abstract: This paper describes a metallographic preparation of the heat-exchanger austenitic stainless steels, i.e., SUPER 304H, HR3C and Sanicro 25. The as-received materials delivered after the solution annealing are very resistant to the chemical etchants. Therefore, it is more efficient to optimize the parameters of the electrolytic etching in the acidic or basic electrolytes. After the materials’ operation under elevated temperatures (600–750 °C), the microstructure is easier to etch due to the reduction of corrosion resistance. For the following analyses, it is necessary to think of the etching purpose in advance. For the grain size determination, it is sufficient to use electrolytic etching in the oxalic acid solution or chemical swabbing in the combination of 15 ml HCl, 10 ml acetic acid and 5 ml HNO₃. For the image analysis of the intermetallics, the previous methods can be too invasive and give skewed results. In many cases, this leads to the overetching and thus removal of the observed particles (intermetallics, carbides, etc.). It is suitable to use selective etching methods or only polishing for a more precise evaluation, e.g., electron microscopy.

Abstract: Photochemical machining (PCM) is an emerging method for machining of very thin and difficult-to-cut material with complex geometrical profile. PCM is one of recommended method for machining of aerospace components, biomedical appliances, electronics part and decorative items. High corrosion resistance, better life, good appearance and strength recommend SS-430 as suitable material for various applications. In the current investigation, the parametric investigations of process parameters in photochemical machining for concentration and temperature of etchant, time of etching is done through ANOVA analysis. Grey Relational Analysis is performed to estimate the optimum machining parameters during PCM of SS-430. Formulation of mathematical model is done for prediction of results. Taguchi (L₂₇) experimental array is used for Design of Experiments (DoE). The significance process parameters are estimated to govern the process with F-Values. Confirmatory test is conducted to observe the improvement in the responses. ANN predictive model is built up for investigation of error between predictive and experimental values. The obtained optimum set is used for manufacturing of micromesh typically used in smoke detector to safeguard human life.

Abstract: MXene is the new family of two-dimensional (2D) transition metal carbides, carbonitrides and nitrides discovered in 2011. The unique properties of 2D MXene such as excellent mechanical properties, hydrophilic surfaces and metallic conductivity made it interesting for application in electrodes of rechargeable batteries, supercapacitors, photocatalysts, catalysts, transparent conducting films, and flexible high-strength composites. The MXene can be synthesized through a selective etching process by using either in-situ HF (hydrofluoric acid) or direct HF methods. This study reports on the effect of the in-situ HF and direct HF etching procedures on the morphology of the synthesis Ti₂C₃ MXene using titanium aluminum carbide (Ti₂AlC₃) as precursor. The morphology and elements presence were evaluated by using variable pressure field emission scanning electron microscope (FESEM) and energy dispersion X-ray (EDX) spectroscopy analyses, respectively. The analysis shows that the MXene synthesized through the direct HF method was successfully delaminated compared to the in-situ HF procedures.

Abstract: Tetramethylammonium hydroxide (TMAH) is a metal-free strong alkaline solution which can etch poly-Si. The concentration of dissolved gas as well as the concentration of TMAH affects etching rate of poly-Si. The detailed kinetics of poly-Si etching in TMAH solution is investigated in this study. The effect of water and TMAH concentration on the etching kinetics of poly-Si was investigated by using various concentrations of TMAH solution. It is found that H₂O in TMAH solution plays an important role in etching poly-Si. Presence of dissolved CO₂ and O₂ in TMAH solution tends to inhibit etching of poly-Si. The concentration of dissolved CO₂ and O₂ in TMAH were reduced by Ar bubbling, thereby the poly-Si etching rate increased.