• Journal of the Korean Vacuum Society
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• v.6 no.4
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• pp.364-371
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• 1997

Silicon trench etching has been carried out using a magnetically enhanced reactive ion etching system in HBr plasma containing He-$O_2$, $CF_4$. The changes of etch rate and etch profile, the degree of residue formation, and the change of surface chemical state were investigated as a function of additive gas flow rate. A severe lateral etching was observed when pure HBr plasma was used to etch the silicon, resulted in a pot shaped trench. When He-$O_2$, $SiF_4$ additives were added to HBr plasma, the lateral etching was almost eliminated and a better trench etch profile was obtained. The surface etched in HBr/He-$O_2/SiF_4$ plasma showed relatively low contamination and residue elements compared to the surface etched in HBr/He-$O-2/CF_4$plasma. In addition, the etching characteristics including low residue formation and chemically clean etched surface were obtained by using HBr containing He-$O_2$ or $SiF_4$ additive gases instead of $CF_4$ gas, which were confirmed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM).

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.454-454
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• 2014

Silicon microwire array is one of the promising platforms as a means for developing highly efficient solar cells thanks to the enhanced light trapping efficiency. Among the various fabrication methods of microstructures, deep reactive ion etching (DRIE) process has been extensively used in fabrication of high aspect ratio microwire arrays. In this presentation, we show precisely controlled Si microwire arrays by tuning the DRIE process conditions. A periodic microdisk arrays were patterned on 4-inch Si wafer (p-type, $1{\sim}10{\Omega}cm$) using photolithography. After developing the pattern, 150-nm-thick Al was deposited and lifted-off to leave Al microdisk arrays on the starting Si wafer. Periodic Al microdisk arrays (diameter of $2{\mu}m$ and periodic distance of $2{\mu}m$) were used as an etch mask. A DRIE process (Tegal 200) is used for anisotropic deep silicon etching at room temperature. During the process, $SF_6$ and $C_4F_8$ gases were used for the etching and surface passivation, respectively. The length and shape of microwire arrays were controlled by etching time and $SF_6/C_4F_8$ ratio. By adjusting $SF_6/C_4F_8$ gas ratio, the shape of Si microwire can be controlled, resulting in the formation of tapered or vertical microwires. After DRIE process, the residual polymer and etching damage on the surface of the microwires were removed using piranha solution ($H_2SO_4:H_2O_2=4:1$) followed by thermal oxidation ($900^{\circ}C$, 40 min). The oxide layer formed through the thermal oxidation was etched by diluted hydrofluoric acid (1 wt% HF). The surface morphology of a Si microwire arrays was characterized by field-emission scanning electron microscopy (FE-SEM, Hitachi S-4800). Optical reflection measurements were performed over 300~1100 nm wavelengths using a UV-Vis/NIR spectrophotometer (Cary 5000, Agilent) in which a 60 mm integrating sphere (Labsphere) is equipped to account for total light (diffuse and specular) reflected from the samples. The total reflection by the microwire arrays sample was reduced from 20 % to 10 % of the incident light over the visible region when the length of the microwire was increased from $10{\mu}m$ to $30{\mu}m$.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1529_1530
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• 2009

The process conditions for fabricating p-type silicon pillars were optimized by controlling current density, bath temperature. To get best process flexibility for pillar arrays formation, three factors affecting pillar formation were changed. First, the solution bath was designed to keep constant temperature during the experiment irrespective of external temperature. Second, the counter Pt electrode was changed from rod type to mesh to obtain uniform distribution of current density. Third, Cr-Cu alloy electrode instead of Cu was used to increase electrode current density.

• Journal of Fisheries and Marine Sciences Education
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• v.19 no.3
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• pp.366-372
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• 2007

This paper presents the fabrication techniques of microcooling fins for microelectronics applications. The various types of cooling fins have been fabricated on the surface of a silicon wafer (4inch-N type) by using wet etching technique. The designed micro fins and micro channels are considered as an effective method for cooling microelectronics devices generating high heat flux. Further we extensively investigate the design processes fabricating micro fins and channels which can cool the heat generated from high density electronics devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.3
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• pp.276-283
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• 1994

The dislocation configuration in web-grown silicon ribbon was investigated using chemical etching techniques. The presence of dislocation loops on twin planes is observed and acounted for by self-interstitial condensation. The interstitials were either quenched in, due to the rapid cooling of the ribbon from the solidification temperatures, or produced by oxide precipitation on the twin plane. Very large faulted loops of mm size were also observed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.30-35
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• 2013

In order to increase cell efficiency in crystalline silicon solar cell, reduction of light reflection is one of the essential problem. Until now silicon wafer was textured by wet etching process which has random patterns along crystal orientation. In this study, high aspect ratio patterns are manufactured by nano imprint process and reflectance could be minimized under 1%. After that, screen printed solar cell was fabricated on the textured wafer and I-V characteristics was measured by solar simulator. Consequently cell efficiency of solar cell fabricated using the wafer textured by nano imprint process increased 1.15% than reference solar cell textured by wet etching. Internal quantum efficiency was increased in the range of IR wave length but decreased in the UV wavelength. In spite of improved result, optimization between nano imprinted pattern and solar cell process should be followed.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.138-140
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• 2006

A new diagnosis model was constructed by combining atomic force microscopy (AFM), wavelet, and neural network. Plasma faults were characterized by filtering AFM-measured etch surface roughness with wavelet. The presented technique was evaluated with the data collected during the etching of silicon oxynitride thin film. A total of 17 etch experiments were conducted. Applying wavelet to AFM, surface roughness was detailed into vertical, horizon%at, and diagonal components. For each component, neural network recognition models were constructed and evaluated. Comparisons revealed that the vertical component-based model yielded about 30% improvement in the recognition accuracy over others. The presented technique was evaluated with the data collected during the etching of silicon oxynitride thin film. A total of 17 etch experiments were conducted

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1977-1979
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• 1996

Single-crystaIline silicon diaphgrams and features are fabricated without using an etch stop process. The process involves vertical dry etching, double-sided alignment, followed by wet-chemical etching from the back side. The abvantages of this process are that $5{\sim}50{\mu}m$ diaphgrams and features can be fabricated accurately and inexpensively. In addition, since no impurity-based process is introduced, highly uniform and homogenous properties can be achieved

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.221-222
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• 2008

In Crystalline Si solar cells, Anti-Reflection Coating is contribute to improvement in energy conversion efficiency due to decrease of optical loss and recombination owing to surface passivation. Porous Si is formed electrochemical etching that uses chemical solution and anodization etching. So It gives that advantage in rapid process time and without high cost equipment. In this paper, We compare Porous Si with $SiO_2$/SiNx ARC and analyze that by anti-reflection coating.

• International Journal of Precision Engineering and Manufacturing-Green Technology
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• v.5 no.5
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• pp.631-636
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• 2018

Extraction of photosynthetic currents from thylakoids was studied using micro pillar structured electrode. Thylakoids were isolated from spinach leaves, and the size and shape of thylakoids were estimated from scanning electron microscopy images. Based on the geometry information of thylakoids, micro pillar shaped electrode was designed and fabricated using metal-assisted chemical etching of silicon wafers. Influence of photovoltaic effect on the silicon-based micro pillar electrode was confirmed to be negligible. Photosynthetic currents were measured in a three-electrode setup with an electron mediator, potassium ferricyanide. Photosynthetic currents from micro pillar electrodes were enhanced compared with the currents from flat electrodes. This indicates the significance of the enhanced contact between thylakoids and an electrode for harvesting photosynthetic electrons.