• Journal of the Korean Society for Precision Engineering
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• v.20 no.6
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• pp.27-36
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• 2003

The Electro-Rheological (ER) fluid has been used to the ultraprecision polishing of single crystal silicon as new polishing slurry whose properties such as yield stress and particle structure changed with the application of an electric field. In this work, it is aimed to find the effective parameters in the ER fluid on material removal in the polishing system whose structure is similar to that of the simple hydrodynamic bearing. The generated pressure in the gap between a moving wall and a workpiece, as well as the electric field-induced stress of the mixture of ER fluid-abrasives, is evaluated experimentally, and their influence on the polishing of single crystal silicon is analyzed. Moreover, the behavior of abrasive and ER particles is described.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.2
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• pp.32-38
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• 2004

The electrorheological(ER) fluid has been used to the ultraprecision polishing of single crystal silicon as new polishing slurry whose properties such as yield stress and particle structure changed with the application of an electric field. In this work, it is aimed to find the effective parameters in the ER fluid on material removal in the polishing system whose structure is similar to that of the simple hydrodynamic bearing. The generated pressure in the gap between a moving wall and a workpiece, as well as the electric field-induced stress of the mixture of ER fluid-abrasives, is evaluated experimentally, and their influence on the polishing of single crystal silicon is analyzed. Moreover, the behavior of abrasive and ER particles is described.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.122-123
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• 2002

Cu CMP process control for global planarization of semiconductor surface were studied on a platen polisher by using an experimental copper slurry containing ceria as the abrasive component. In order to understand the process. a design of experiment was conducted. From the experiment. the effects of polishing parameters such as polishing pressure, platen speed, and speed of wafer carrier on the removal rate of copper and the uniformity in copper removal were calculated and discussed. In this study, process parameters of Cu CMP and WIWNU(Within Wafer Non Uniformity) were presented.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.5
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• pp.149-158
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• 2002

Recently, the minimum line width shows a tendency to decrease and the multi-level increases in semiconductor. Therefore, a planarization technique is needed and chemical mechanical polishing(CMP) is considered as one of the most suitable process. CMP accomplishes a high polishing performance and a global planarization of high quality. However there are several defects in CMF, such as micro-scratches, abrasive contaminations and non-uniformity of polished wafer edges. Wet etching process including spin-etching can eliminate the defects of CMP. It uses abrasive-free chemical solution instead of slurry. On this study, ILD(Interlayer-Dielectric) was removed by CMP and wet etching process using DHF(Diluted HF) in order to investigate the possibility of planrization by wet etching mechanism. In the thin film wafer, the results were evaluated from the viewpoint of material removal rate(MRR) and within wafer non-uniformity(WIWNU). And the pattern step heights were also compared for the purpose of planarity characterization of the patterned wafer. Moreover, Chemical polishing process which is the wet etching process with mechanical energy was introduced and evaluated for examining the characteristics of planarization.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.863-867
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• 2014

In this study, an acoustic emission (AE) sensor was used for measuring the abrasive and molecular-scale phenomena in chemical mechanical polishing (CMP). An AE sensor is a transducer that converts a mechanical wave into an electrical signal, and is capable of acquiring high-level frequencies from materials. Therefore, an AE sensor was installed in the CMP equipment and the signals were measured simultaneously during the polishing process. In this study, an AE monitoring system was developed for investigating the sensitivity of the AE signal to (a) the variations in the material properties of the pad, slurry, and wafer and (b) the change in conditions during the CMP process. This system was adapted to Oxide and Cu CMP processes. AE signal parameters including AE raw frequency, FFT, and amplitude were analyzed for understanding the abrasive and molecular-level phenomena in the CMP process. Finally, we verified that AE sensors with different bandwidths could function in complementary ways during CMP process monitoring.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.6
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• pp.225-229
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• 2011

Most of the silicon cutting methods using the multi-wire with the slurry injection have been used for wafers of the crystalline solar cell. But the productivity of slurry injection cutting type falls due to low cutting speeds. Also, the direct contact with the metal wire and silicon block increases the concentration of metallic impurities in the wafer's surface. In addition, the abrasive silicon carbide (SiC) generates pollutants. And production costs are rising because it does not re-use the worn wire. On the other hand, the productivity of the cutting method using the diamond coated wire is about 2 times faster than the slurry injection cutting type. Also, the continuous cutting using the used wire of low wear is possible. And this is a big advantage for reduced production costs. Therefore, the cutting method of the diamond coated wire is more efficient than the slurry injection cutting technique. In this study, each cutting type is analyzed using the surface characteristics of the solar wafer and will describe the effects of the manufacturing process of the solar cell. Finally, we will suggest improvement methods of the solar cell process for using the diamond cutting type wafer.

• Design & Manufacturing
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• v.13 no.3
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• pp.12-18
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• 2019

Fluid jet polishing is a method of jetting a fluid to polish a concave or free-form surface. However, the fluid jet method is difficult to form a stable polishing spot because of the lack of concentration. In order to solve this problem, MR fluid jet polishing system using an abrasive mixed with an MR fluid whose viscosity changes according to the intensity of a magnetic field is under study. MR fluid jet polishing is not easy to formulate for precise optimal conditions and material removal due to numerous fluid compositions and process conditions. Therefore, in this paper, quantitative data on the factors that have significant influence on the machining conditions are presented using various simulations and the correlation studies are conducted. In order to verify applicability of the fabricated MR fluid jet polishing system by nozzle diameter, the flow pattern and velocity distribution of MR fluid and polishing slurry of MR fluid jet polishing were analyzed by flow analysis and shear stress due to magnetic field changes was analyzed. The MR fluid of the MR fluid jet polishing and the flow pattern and velocity distribution of the polishing slurry were analyzed according to the nozzle diameter and the effects of nozzle diameter on the polishing effect were discussed. The analysis showed that the maximum shear stress was 0.45 mm at the diameter of 0.5 mm, 0.73 mm at 1.0 mm, and 1.24 mm at 1.5 mm. The cross-sectional shape is symmetrical and smooth W-shape is generated, which is consistent with typical fluid spray polishing result. Therefore, it was confirmed that the high-quality surface polishing process can be stably performed using the developed system.

• Advances in materials Research
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• v.1 no.2
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• pp.129-146
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• 2012

Polycrystalline diamond is an ideal material for parts with micro-holes and has been widely used as dies and cutting tools in automotive, aerospace and woodworking industries due to its superior wear and corrosion resistance. In this research paper, the modeling and simultaneous optimization of multiple performance characteristics such as material removal rate and surface roughness of polycrystalline diamond (PCD) with ultrasonic machining process has been presented. The fuzzy logic and taguchi's quality loss function has been used. In recent years, fuzzy logic has been used in manufacturing engineering for modeling and monitoring. Also the effect of controllable machining parameters like type of abrasive slurry, their size and concentration, nature of tool material and the power rating of the machine has been determined by applying the single objective and multi-objective optimization techniques. The analysis of results has been done using the MATLAB 7.5 software and results obtained are validated by conducting the confirmation experiments. The results show the considerable improvement in S/N ratio as compared to initial cutting conditions. The surface roughness of machined surface has been measured by using the Perthometer (M4Pi, Mahr Germany).

• Transactions on Electrical and Electronic Materials
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• v.8 no.1
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• pp.26-31
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• 2007

The goal of this study is to determine if High Pressure Micro Jet (HPMJ) conditioning can be used as a substitute for, or in conjunction with, conventional diamond pad conditioning. Five conditioning methods were studied during which 50 ILD wafers were polished successively in a 100-mm scaled polisher and removal rate (RR), coefficient of friction (COF), pad flattening ratio (PFR) and scanning electron microscopy (SEM) measurements were obtained. Results indicated that PFR increased rapidly, and COF and removal rate decreased significantly, when conditioning was not employed. With diamond conditioning, both removal rate and COF were stable from wafer to wafer, and low PFR values were observed. SEM images indicated that clean grooves could be achieved by HPMJ pad conditioning, suggesting that HPMJ may have the potential to reduce micro scratches and defects caused by slurry abrasive particle residues inside grooves. Regardless of different pad conditioning methods, a linear correlation was observed between temperature, COF and removal rate, while an inverse relationship was seen between COF and PFR.

• Tribology and Lubricants
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• v.34 no.3
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• pp.115-122
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• 2018

Chemical mechanical polishing (CMP) is a hybrid processing method in which the surface of a wafer is planarized by chemical and mechanical material removal. Since mechanical material removal in CMP is caused by the rolling or sliding of abrasive particles, interfacial friction during processing greatly influences the CMP results. In this paper, the trend of tribology research on CMP process is discussed. First, various friction force monitoring methods are introduced, and three elements in the CMP tribo-system are defined based on the material removal mechanism of the CMP process. Tribological studies on the CMP process include studies of interfacial friction due to changes in consumables such as slurry and polishing pad, modeling of material removal rate using contact mechanics, and stick-slip friction and scratches. The real area of contact (RCA) between the polishing pad and wafer also has a significant influence on the polishing result in the CMP process, and many researchers have studied RCA control and prediction. Despite the fact that the CMP process is a hybrid process using chemical reactions and mechanical material removal, tribological studies to date have yet to clarify the effects of chemical reactions on interfacial friction. In addition, it is necessary to clarify the relationship between the interface friction phenomenon and physical surface defects in CMP, and the cause of their occurrence.