• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1121-1124
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• 2001

In this study, we verify th effects of pattern density on interlayer dielectric chemical mechanical polishing process based on the analysis of Preston's equation and confirm this analysis by several experiments. Appropriate modeling equation, transformed form Preston's equations used in glass polishing, will be suggested and described the effects of this modeling during pattern wafer ILD CMP. Results indicate that the modeling is well agreed to middle density structure of the die in pattern wafer, but has some error in low and high density structure of the die. Actually, the die used in Fab, was designed to have a appropriate density, therefore this modeling will be suitable for estimating the results of ILD CMP.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.767-768
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• 2011

• Tribology and Lubricants
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• v.27 no.1
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• pp.7-12
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• 2011

Interest in advanced machining process such as AJM(abrasive jet machining) and CMP(chemical-mechanical polishing) using micro/nano-sized abrasives has been on the increasing demand due to wide use of super alloys, composites, semiconductor and ceramics, which are difficult to or cannot be processed by traditional machining methods. In this paper, the effects of pressure, wafer moving velocity and fluid viscosity were investigated by 2-dimensional finite element analysis method considering slurry fluid flow. From the investigation, it could be found that the simulation results quite corresponded well to the Preston's equation that describes pressure/velocity dependency on material removal. The result also revealed that the stress and corresponding material removal induced by the collision of particle may decrease under relatively high wafer moving speed due to the slurry flow resistance. In addition, the increase in slurry fluid viscosity causes the reduction of material removal rate. It should be noted that the viscosity effect can vary with the shape of abrasive particle.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.311-315
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• 2001

This paper presents the result of basic study about corrective polishing for arbitrary surface figure. In this study, we researched polishing characteristics on the working condition of optical glass. The abrasive size, relative velocity and working pressure were selected major factors that affect polishing process. The Preston's equation which is the representative model of polishing process was used to model the unit removal shape. The Preston's coefficient and unit removal function were calculated from the polished surface. Applying these results, we have shown that the systematic corrective polishing of arbitary figure is feasible through experiments and analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.227-230
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• 2004

As the organic acids were added in the slurry, zeta potential of alumina was changed to negative value and IEP value was shifted from alkaline to acidic pH. In citric acid based slurry, Cu surface continuously dissolved and etching depth linearly increased. On the contrary, passivation layer was grown on Cu surface in oxalic acid based slurry. As the platen rotation speed increased, Preston coefficient decreased in both slurries. With oxalic acid based slurry, at low velocity, removal rate is high value because of high friction force compared to citric acid based slurry. As platen velocity increased, removal of Cu in citric acid based slurry became higher value than oxalic acid based slurry. Typical lubrication behaviors were observed in both slurries. As Sommerfeld number increased, COF values gradually decreased and then re-increased. It indicated that lubrication was changed to direct contact or semi-direct contact mode to hydro-lubrication mode.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.65-71
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• 2001

The development process of the polishing system for the aspherical lens mold for opto-electronics industry is described. The system uses the method that polishing tool is scanned on the surface under PC-NC control for the aspherical lens mold. The two axes interpolation of the minimum translation mechanism is applied to give uniform working condition by motion analysis. An aspherical surface is divided into multiple sections and each dwell time is calculated from the polishing rate model based on the Preston equation. As result of form error compensation experiment, initial form error is decreased about 25% while an average value of surface roughness is also reduced successfully from 180nm to 19nm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.497-498
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• 2006

Tribological properties of a Magneto-Rheological(MR) fluid in a polishing process are studied. For this polishing process, abrasive wear model is proposed as a function of shear force, normal force and actual mean velocity of MR particles at workpiece surface. Experimental conditions are changed by varying the gap distance between workpiece and tool and the rotational speed of tool. From the experimental results, a modified Stribeck curve is obtained, and the friction coefficient turns out to have linear relationship with a modified Sommerfeld number. The validity of the wear model is supported by additional experiments performed for measuring material removal rates.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.196-203
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• 2002

Generally, non-uniformity and removal rate are important factors on measurements of both wafer and die scale. In this study, we verify the effects of the pressure and relative velocity on the results of the chemical mechanical polishing and the effect of pattern density on inter layer dielectric chemical mechanical polishing of patterned wafer. We suggest an appropriate modeling equation, transformed from Preston\`s equations which was used in glass polishing, and simulate the removal rate of patterned wafer in chemical mechanical polishing. Results indicate that the pressure and relative velocity are dominant factors for the chemical mechanical polishing and pattern density effects on removal rate of pattern wafers in die scale. The modeling is well agreed to middle and low density structures of the die. Actually, the die used in Fab. was designed to have an appropriate density, therefore the modeling will be suitable for estimating the results of ILD CMP.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.4
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• pp.301-306
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• 2016

High speed polishing can kinematically increase the polishing removal rate by using the conventional Preston equation, especially for hard substrates such as sapphire or diamond. However, high speed effects should be clarified beforehand considering the lubrication state and process parameter variations. In this paper, we developed a polishing experimental method and apparatus to determine the lubrication state by measuring the real time friction coefficient using two load cells. Through experiments, we obtained a boundary lubrication state above 0.35 of the friction coefficient by using low table speed and high polishing load, indicating a synchronized stable behavior in polishing head rotation. However, larger Stribeck indexes by a high speed above 200 rpm can generate a hydrodynamic lubrication state below 0.25 of the low friction coefficient. This causes the polishing head rotation to stop. A forced and synchronized head rotation is required for high speed polishing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.35-37
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• 2005

100, 200nm 크기의 colloidal silica 각각에 나노 ceria 입자를 수열합성법으로 코팅하였다. Colloidal silica 입자에 ceria를 코팅 시 slurry의 pH조절과 수열처리에 이용하여 silica에 ceria가 코팅됨을 TEM과 zeta-potential을 이용하여 확인하였다. 연마 슬러리의 분산 안정성과 연마효율을 높이기 위하여 슬러리의 pH 는 9로 하였으며, 이때의 zeta-potential 값은 -25 mV이었다. 1 wt%로 제조된 연마슬러리를 이용하여, 4 inch $SiO_2$, $Si_3N_4$ wafer를 압력변화에 따른 연마특성을 관찰 하였다. Ceria coated colloidal silica 100 nm, 200 nm와 commercial한 $CeO_2$입자를 연마압력 6 psi로 oxide film을 연마한 결과 연마율이 각각 2490 ${\AA}/min$, 4200 ${\AA}/min$, 4300 ${\AA}/min$으로 측정되었다. 또한 $SiO_2$, $Si_3N_4$ film의 6 psi압력에서 ceria coated colloidal silica 100 nm, 200 nm와 commercial 한 $CeO_2$입자의 선택비는 3, 3.8, 6.7 이었다. 입자크기가 클수록 연마율이 높으며, Preston equation을 따라 연마 압력과 연마율이 비례하였다.