• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3310-3312
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• 1999

We have studied the method of silicon direct bonding using the mixture of $HNO_$, $H_2O_2$, and HF chemicals called the controlled slight etch (CSE) solution for the effective wafer cleaning. CSE, two combinations of oxidizing and etching agents, have been used to clean the silicon surfaces prior to wafer bonding. Two wafers of silicon and silicon dioxide were contacted each other at room temperature and postannealed at $300{\sim}1100^{\circ}C$ in $N_2$ ambient for 2.5 h. We have cleaned silicon wafers with the various HF concentrations and characterized the parameters with regard to surface roughness, chemical nature, chemical oxide thickness, and bonding energy. It was observed that the chemical oxide thickness on silicon wafer decreased with increasing HF concentrations. The initial interfacial energy and final energy postannealed at $1100^{\circ}C$ for 2.5h measured by the crack propagation method was 122 $mJ/m^2$ and 2.96 $mJ/m^2$, respectively.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2410-2412
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• 2005

In this study, two types of PS substrate were fabricated for sensing of chemical and biological substances. For sensing of the humidity and chemical analyzes such as $CH_3OH$ or $C_2H_5OH$, PS layers are prepared by photoelectrochemical etching of silicon wafer in aqueous hydrofluoric acid solution. To evaluate their sensitivity, we measured the resistance variation of the PS diaphragm. As the amplitude of applied voltage increases from 2 to 6Vpp at constant frequency of 5kHz, the resistance variation for humidity sensor rises from 376.3 to $784.8{\Omega}$/%RH. And the sensitivities for $CH_3OH$ and $C_2H_5OH$ were 0.068 uA/% and 0.212 uA/%, respectively. For biological sensing application, amperometric urea sensors were fabricated based on porous silicon(PS), and planar silicon(PLS) electrode substrates by the electrochemical methods. Pt thin film was sputtered on these substrates which were previously formed by electrochemical anodization. Poly (3-methylthiophene) (P3MT) were used for electron transfer matrix between urease(Urs) and the electrode phase, and Urs also was by electrochemically immobilized. Effective working area of these electrodes was determined for the first time by using $Fe(CN)_6^{3-}/Fe(CN)_6^{4-}$ redox couple in which nearly reversible cyclic voltammograms were obtained. The $i_p$ vs $v^{1/2}$ plots show that effective working electrode area of the PS-based Pt thin film electrode was 1.6 times larger than the PLS-based one and we can readily expect the enlarged surface area of PS electrode would result in increased sensitivity by ca. 1.6 times. Actually, amperometric sensitivity of the Urs/P3MT/Pt/PS electrode was ca 0.91uA/$mM{\cdot}cm^2$, and that of the Urs/P3MT/Pt/PLS electrode was ca. 0.91uA/$mM{\cdot}cm^2$ in a linear range of 1mmol/L to 100mmol/L urea concentrations

• Journal of Sensor Science and Technology
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• v.19 no.4
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• pp.291-296
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• 2010

Recently, recycling method of waste wafer has been an area of solar cell to cut costs. Micro_blasting is one of the promising candidates for recycling of waste wafer due to their extremely simple and cost-effective process. In this paper, we attempt to explore the effect of micro_blasting and DRE(damage removal etching) process for solar cell. The optimal process conditions of micro_blasting are as follows: $10{\mu}m$ sized $Al_2O_3$ powder, jetting pressure of 400 kPa, and scan_speed of 30 cm/s. And the particles formed on micro_blasted wafer were removed by DRE precess which was performed by using HNA(HF/$HNO_3$/$CH_3COOH$) and TMAH(tetramethyl ammonium hydroxide). Structural analysis was done using a-step and the XRD patterns.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.85-90
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• 2000

For more esthetic treatments the use of composite in molar areas are increasing. But polymerzation shrinkage that cause marginal leakage and cuspal deflection has been the problems of composites. The purpose of this study is to compare the effect of low intensity curing and polishing period on marginal leakage. Cavities were prepared on the buccal or lingual surface of forty five sound extracted human teeth and etching, application of bonding agent and filling of composite was done. Group 1 was light cured at intensity of 600$mW/cm^2$ for 41 seconds and polished. Group 2 was light cured at intensity of 300$mW/cm^2$ for 2 seconds and polished and after polishing it was light cured for 40 seconds at 600$mW/cm^2$. Group 3 was light cured at intensity of 300$mW/cm^2$ for 2 seconds and waited for 5 minutes and after curing at 600$mW/cm^2$ for 40 seconds polishing was done. The specimens were thermocycled at $5^{\circ}C$ and $55^{\circ}C$ for 1000 cycles and immersed in 2% methylene blue solution for 24 hours. Composite-tooth interface was examined under stereobinocular microscope for dye penetration. The results were as follows : 1. Group which were cured at low intensity and polished after curing at high intensity showed less marginal leakage than group which were cured at high intensity for 41 seconds(p<0.05). 2. Marginal leakage between group which were cured at low intensity and polished immediately and group which were cured at high intensity for 41 second were not significantly different. Light curing at low intensity can reduce marginal leakage but polishing immediately after curing at low intensity for short time can affect marginal leakage.

• Korean Journal of Materials Research
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• v.16 no.12
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• pp.731-738
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• 2006

It is seriously considered using Al CMP (chemical mechanical planarization) process for the next generation 45 nm Al wiring process. Al CMP is known that it has a possibility of reducing process time and steps comparing with conventional RIE (reactive ion etching) method. Also, it is more cost effective than Cu CMP and better electrical conductivity than W via process. In this study, we investigated 4 different kinds of slurries based on abrasives for reducing scratches which contributed to make defects in Al CMP. The abrasives used in this experiment were alumina, fumed silica, alkaline colloidal silica, and acidic colloidal silica. Al CMP process was conducted as functions of abrasive contents, $H_3PO_4$ contents and pressures to find out the optimized parameters and conditions. Al removal rates were slowed over 2 wt% of slurry contents in all types of slurries. The removal rates of alumina and fumed silica slurries were increased by phosphoric acid but acidic colloidal slurry was slightly increased at 2 vol% and soon decreased. The excessive addition of phosphoric acid affected the particle size distributions and increased scratches. Polishing pressure increased not only the removal rate but also the surface scratches. Acidic colloidal silica slurry showed the highest removal rate and the lowest roughness values among the 4 different slurry types.

• Korean Journal of Materials Research
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• v.19 no.7
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• pp.349-355
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• 2009

Metal thin film patterns on a LTCC substrate, which was connected through inner via and metal paste for electrical signals, were formed by a screen printing process that used electric paste, such as silver and copper, in a conventional method. This method brought about many problems, such as non uniform thickness in printing, large line spaces, and non-clearance. As a result of these problems, it was very difficult to perform fine and high resolution for high frequency signals. In this study, the electric signal patterns were formed with the sputtered metal thin films (Ti, Cu) on an LTCC substrate that was coated with protective oxide layers, such as $TiO_2$ and $SiO_2$. These electric signal patterns' morphology, surface bonding strength, and effect on electro plating were also investigated. After putting a sold ball on the sputtered metal thin films, their adhesion strength on the LTCC substrate was also evaluated. The protective oxide layers were found to play important roles in creating a strong design for electric components and integrating circuit modules in high frequency ranges.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2187-2193
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• 2002

We present a novel method for 3D microfabrication with LIGA process that utilizes a deep X-ray mask in which a micro-actuator is integrated. The integrated micro-actuator oscillates the X-ray absorber, which is formed on the shuttle mass of the micro-actuator, during X-ray exposures to modify the absorbed dose profile in X-ray resist, typically PMMA. 3D PMMA microstructures according to the modulated dose contour are revealed after GG development. An X-ray mask with integrated comb drive actuator is fabricated using deep reactive ion etching, absorber electroplating, and bulk micromachining with silicon-on-insulator (SOI) wafer. 1mm $\times$ 1 mm, 20 $\mu$m thick silicon shuttle mass as a mask blank is supported by four 1 mm long suspension beams and is driven by the comb electrodes. A 10 $\mu$m thick, 50 $\mu$m line and spaced gold absorber pattern is electroplated on the shuttle mass before the release step. The fundamental frequency and amplitude are around 3.6 kHz and 20 $\mu$m, respectively, for a do bias of 100 V and an ac bias of 20 $V_{p-p}$ (peak-peak). Fabricated PMMA microstructure shows 15.4 $\mu$m deep, S-shaped cross section in the case of 1.6 kJ $cm^{-3}$ surface dose and GG development at 35$^{\circ}C$ for 40 minutes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.3
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• pp.549-554
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• 2007

In this paper, the luminance and resistance from different electrode materials of external electrode fluorescent lamp are measured and analyzed. New materials and process technology of external electrode are very important for the developed characteristics in lamp fabrication. This experiment, three different types for the forming of external electrode are Cu and Al taping, silver paste, Ni and Cu electrode-less plating methods. In the measurement of luminance, the results of brightness by Ni and Au plating methods for the external electrode on lamp glass are presented and also compared with the results by the methods using different electrode materials. The measured resistance values of Ni and Au plating process showed a little bit higher than that of silver paste process in spite of developed results of brightness. The Ni and Ni/Au plating processes are demonstrated best results and also showed a little bit different brightness due to different previous surface etching treatments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.10
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• pp.1306-1311
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• 2020

In this study, we proposed an anti-reflective nano-structure to improve the photoresponsivity of AlGaN UV photodiode that can be used as a receiver in a solar blind UV optical communication system. The anti-reflective nano-structure was fabricated by forming Ni nano-clusters on SiO2 film followed by etching the underneath SiO2 film. A sample with the anti-reflective nano-structure exhibited lower surface reflection along with less dependency on the wavelength in comparison with a sample without the nano-structure. Finally, a UV photodiode was fabricated by applying an anti-reflective structure produced by heat-treating a 2 nm-thick Ni layer. The photodiode fabricated with the proposed nano-structure exhibited noticeable improvement in the photoresponsivity at the wavelength range from 240 nm to 270 nm in comparison with the same photodiode with a SiO2 film without the nano-structure.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.72-77
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• 2021

The radial distribution of etch rate was analyzed using the ion energy flux model in VHF-CCP. In order to exclude the effects of polymer passivation and F radical depletion on the etching. The experiment was performed in Ar/SF6 plasma with an SF6 molar ratio of 80% of operating pressure 10 and 20 mTorr. The radial distribution of Ar/SF6 plasma was diagnosed with RF compensated Langmuir Probe(cLP) and Retarding Field Energy Analyzer(RFEA). The radial distribution of ion energy flux was calculated with Bohm current times the sheath voltage which is determined by the potential difference between the plasma space potential (measured by cLP) and the surface floating potential (by RFEA). To analyze the etch rate uniformity, Si coupon samples were etched under the same condition. The ion energy flux and the etch rate show a close correlation of more than 0.94 of R² value. It means that the etch rate distribution is explained by the ion energy flux.