• Journal of the Korean Society for Precision Engineering
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• v.29 no.12
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• pp.1285-1289
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• 2012

This study has been focused on application of ELID lapping process for mirror-surface machining of sapphire wafer. Sapphire wafer is a superior material with optic properties of high performance as light transmission, thermal conductivity, hardness and so on. High effective surface machining technology is necessary to use sapphire as various usages. The interval ELID lapping process has been set up for lapping of the sapphire material. According to the ELID lapping experimental results, it shows that 12.5 kg of load for lapping is most pertinent to ELID lapping. the surface of sapphire can be eliminated by metal bonded wheel with micron abrasives and the surface roughness of 60 nmRa can be gotten using grinding wheel of 2,000 mesh in 4.5 um, depth of cut. In this study, the chemical experiments after ELID grinding also has been conducted to check chemical reaction between workpiece and grinding wheel on ELID grinding process. It shows that the chemical reaction has not happened as the results of the chemical experiments.

• Journal of Surface Science and Engineering
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• v.32 no.3
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• pp.239-243
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• 1999

At Present, 200mm wafer technology is being applied for commercial fabrications of 64, 128, and 256 M DRAM devices, and 300mm technology will be evolved for 1G DRAM devices in the early 21th century, recognizing limitations of several process technologies. In particular recognition has been realized in harmful effects of surface contamination of trace metals introduced during devicing processes. Such a guide line for surface metal contamination has been proposed as 1E9 and 1E10 atoms/$\textrm{cm}^2$ of individual metal contamination for wafering and devicing of 1G DRAM, respectively, and so its measurement limit should be at least 1E8 atoms/$\textrm{cm}^2$. The detection limit of present measurement systems is 2E9 atoms/$\textrm{cm}^2$ obtainable with TRXFA(Total Reflection X-Ray Fluorescence Analysis). TRXFA is nondestructive and the simplest in terms of operation, and it maps the whole wafer surfaces but needs detection improvement. X-Ray intensity produced with synchrotron accelerator is much higher than that of conventional X-ray sources by order of 4-5 magnitudes. Hence theoretically its reactivity with silicon surfaces is expected to be much higher than the conventional one, realizing improvement of detection limit. X-ray produced with synchrotron accelerator is illuminated at a very low angle with silicon wafer surfaces such as 0.1 degree and reflects totally. Hence informations only from surface can be collected and utilized without overlapping with bulk informations. This study shows the total reflection phenomenon and quantitative improvement of detection limit for metallic contamination. It is confirmed that synchrotron X-ray can be a very promising alternative for realizing improvement of detection limit for the next generation devices.

• Tribology and Lubricants
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• v.26 no.4
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• pp.219-223
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• 2010

Despite the increasing need of nanometer-scale accuracy in abrasive machining using ultrasmall particles such as abrasive jet and chemical mechanical polishing(CMP), the process mechanism is still unknown. Based on the background, research on the effects of various process parameters on the machined surface at abrasive machining was motivated and performed by using finite element analysis where the effect of slurry fluid flow involved. The effect of particle shape on the machined surface during particle-surface collision was discussed in this paper. The results from FEA simulation revealed that any damage or defect generation on machined surface by the impact may occur only if the particle has enough impact energy. Therefore, it could be concluded that generation of the defects and damage on the wafer surface after CMP process was mainly due to direct contact of the 3 bodies, i.e., pad-particle-wafer.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.68-71
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• 2000

In this paper, we have measured the oxygen contents by FTIR in silicon wafer various process technology(slicing, lapping, polishing). The measured data are also compared with the data of etching process(KOH, Bright etching). Also we have measured the surface morpology in backside silicon wafer after etching treatment and etch pit density due to OISF after 4 step high temperature annealing process with optical microscope.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.11
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• pp.2439-2443
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• 2011

To obtain the effect of texturing process in Solar cells, the Si-wafers were textured by using the IPA+DI water mixed etching solution with KOH alkaline. All samples were analyzed by the scanning electron microscopy for the surface images, and it was researched the correlation between the efficiency of optical properties and the effect of texturing. From the results of the surface images obtained by SEM, mc-Si wafer shows a isotropic surface but sc-Si wafers displays the unisotropic surface. The reflectance was improved at the sc-Si wafer textured uniformly, and the reflectance of over etched-samples increased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.5
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• pp.218-223
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• 2001

The chemical-mechanical polishing process was carried out for 2"-dia. sapphire wafer grown by horizontalBridgman method on the urethane lapping pad with the silica sol. The polished wafer shows the full-width at halfmaximum of 200~400 arcsec in double-crystal X-ray diffraction, indicating that the slicing, grinding and lapping processes before the polishing process affected the crystalline structural property of the wafer surface by the mechanical residual stress. For the inclusion of surface treatments after chemical-mechanical polishing such as the thermal annealing at the temperature of $1,200^{\circ}C$for 4 hrs. and chemical etching, the crystalline quality was sigdicantly enhanced with the reduced full-width at half maximum up to 8.3 arcsec.arcsec.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.1
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• pp.25-29
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• 2008

We introduce a new fabrication process for antireflective structured surfaces. A 4-inch silicon wafer was dipped in a suspension of 300-nm-diameter silica particles dispersed in a toluene solution. When the wafer was drawn out of the suspension, a hexagonally packed monolayer structure of particles self-assembled on almost the complete wafer surface. Due to the simple process, this could be applied to micro- and nano-patterning. The self-assembled silica particles worked as a mask for the subsequent reactive ion etching. An array of nanometer-sized pits could be fabricated since the regions that correspond to the small gaps between particles were selectively etched off. As etching progressed, the pits became deeper and combined with neighboring pits due to side-etching to produce an array of cone-like structures. We investigated the effect of etching conditions on antireflection properties, and the optimum shape was a nano-cone with height and spacing of 500 nm and 300 nm, respectively. This nano-structured surface was prepared on a $30\;{\times}\;10-mm$ area. The reflectivity of the surface was reduced 97% for wavelengths in the range 400-700 nm.

• Journal of the Semiconductor & Display Technology
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• v.5 no.3 s.16
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• pp.5-10
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• 2006

This paper investigates cutting qualities after laser dicing and predicts the problems that can be generated by laser dicing. And through 3 point bending test, die strength is measured and the die strength after laser dicing is compared with the die strength after mechanical sawing. Laser dicing is chiefly considered as an alternative to overcome the defects of mechanical sawing such as chipping on the surface and crack on the back side. Laser micromachining is based on the thermal ablation and evaporation mechanism. As a result of laser dicing experiments, debris on the surface of wafer is observed. To eliminate the debris and protect the surface, an experiment is done using a water soluble coating material and ultrasonic. The consequence is that most of debris is removed. But there are some residues around the cutting line. Unlike mechanical sawing, chipping on the surface and crack on the back side is not observed. The cross section of cutting line by laser dicing is rough as compared with that by mechanical sawing. But micro crack can not be seen. Micro crack reduces die strength. To measure this, 3 point bending test is done. The die strength after laser dicing decreases to a half of the die strength after mechanical sawing. This means that die cracking during package assembly can occur.

• New & Renewable Energy
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• v.4 no.2
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• pp.68-73
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• 2008

It is very important that constitution of good hetero-junction interface with a high quality amorphous silicon thin films on very cleaned c-Si wafer for making high efficiency hetero-junction solar cells. For achieving the high efficiency solar cells, the inspection and management of c-Si wafer surface conditions are essential subjects. In this experiment, we analyzed the c-Si wafer surface very sensitively using Spectroscopic Ellipsometer for < ${\varepsilon}2$ > and u-PCD for effective carrier life time, so we accomplished < ${\varepsilon}2$ > value 43.02 at 4.25eV by optimizing the cleaning process which is representative of c-Si wafer surface conditions very well. We carried out that the deposition of high quality hydrogenated silicon amorphous thin films by RF-PECVD systems having high density and low crystallinity which are results of effective medium approximation modeling and fitting using spectroscopic ellipsometer. We reached the cell efficiency 12.67% and 14.30% on flat and textured CZ c-Si wafer each under AM1.5G irradiation, adopting the optimized cleaning and deposition conditions that we made. As a result, we confirmed that spectroscopic ellipsometry is very useful analyzing methode for hetero-junction solar cells which need to very thin and high quality multi layer structure.

• Journal of the Korean Ceramic Society
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• v.28 no.6
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• pp.495-501
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• 1991

This study is intended to make defect-free region, denuded zone at the silicon wafer surface for semiconductor device substrates. In this experiment, initial oxygen concentration of starting material CZ-grown silicon wafer, various heat treatment combinations, denuding ambient and the amounts of oxygen reduction were measured, and then denuded zone (DZ) formation and depth were investigated. In Low/High anneal (DZ formation could be achieved), the optimum temperature for Low anneal was 700$^{\circ}C$∼750$^{\circ}C$. In case of High anneal, with the time increased, DZ depth was increased at 1000$^{\circ}C$, 1150$^{\circ}C$ respectively, but on the contrary, DZ depth was decreased at low temperature 900$^{\circ}C$. As well, out-diffusion time below 2 hours was unsuitable for effective Gettering technique even though the temperature was high, and DZ formation could be achieved when initial oxygen concentration was only above 14 ppm in silicon wafer.