• Membrane and Water Treatment
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• v.4 no.4
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• pp.237-249
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• 2013

Ultra-pure water (UPW), a highly treated water free of colloidal material and of a conductivity less than 0.06 ${\mu}S$, is an essential component required by modern industry. One of the methods for UPW production is the electrodialysis-ion exchange (ED/IE) system, in which the electrodialysis (ED) process is used as a preliminary demineralization step. The IE step can be replaced with electrodeionization (EDI) to decrease the volume of post-regeneration lyes. In this paper, the electrodialysis process carried out to relatively low diluate conductivity was investigated and the costs of UPW production were calculated. The optimal value of desalination degree by ED in the ED/IE and ED/EDI systems was estimated. UPW unit costs for integrated ED/IE and ED/EDI systems were compared to simple ion exchange and other methods for UPW production (RO-IE, RO-EDI). The minimal UPW unit costs in ED/EDI integrated system were estimated as $0.37/$m^3$ for feed TDS 600 mg/L and $0.36/$m^3$ for feed TDS 400 mg/L at 64 $m^3/h$ capacity, which was lower than in the comparable ED/IE integrated system ($0.42-0.44/$m^3$). The presented results suggest that an ED/EDI integrated system may be economically viable.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.391-396
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• 2014

Ultrapure water (UPW) is water containing nothing but water molecule ($H_2O$). The use of UPW is increasing in many industries such as the thermal and nuclear power plants, petrochemical plants, and semiconductor manufacturers. In order to produce UPW, several unit processes such as ion exchange, reverse osmosis (RO), ultraviolet (UV) oxidation should be efficiently arranged. In particular, RO process should remove not only ions but also low molecular weight (LMW) organic matters in UPW production system. But, the LMW organic matter removal data of RO membranes provided by manufacturers does not seem to be reasonable because they tested the removal in high concentration conditions like 1,000 ppm of isopropyl alcohol (IPA, MW=60.1). In this study, bench-scale experiments were carried out using 4-inches RO modules. IPA was used as a model LMW organic matter with low concentration conditions less than 1 ppm as total organic carbon (TOC). As a result, the IPA removal data by manufacturers turned out to be trustable because the effect of feed concentration on the IPA removal was negligble while the IPA removal efficiency became higher at higher permeate flux.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.617-620
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• 1999

To reduce the consumption of chemicals and ultra pure water(UPW) in cleaning process used in device manufacturing, we proposed wet processes that use electrolytic ionized water(EIW), which is generated by electrolysis of a diluted electrolyte solution or UPW and systemically investicate the EIW\`s characteristics. EIW\`s pH values are increased in cathode chamber and decreased in anode chamber according to the electrolysis time and its varied ratio is reduced with time increasement. The variation of pH and ORP is increased accordin to the applied voltage until critical voltage. But more than that voltage, the variation is decreased because of ion\`s scattering effect. When electrolyte is added, the effects of electrolysis is increased because electrolyte acts as catalyst. But when the density of electrolyte is increased more than critical value, ion\`s flowage is obstructed and the effects of electrolysis is decreased.

• Journal of the Semiconductor & Display Technology
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• v.9 no.1
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• pp.55-59
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• 2010

In this study, we developed nonvolatile residue (NVR) real-time monitoring system to measure the nonvolatile residue particle in ultra pure water (UPW). This device has a capability of measuring 4 different channels, i.e., 10 nm, 30 nm, 50 nm, and 100 nm. Until now, the light scattering method to detect RAE(residue after evaporation) was the only choice. However, this method can detect RAE larger than ca. 50 nm. In ultra pure water, RAE particles are usually very small and hard to detect with conventional laser scattering devices. To detect very small RAEs, a new system is developed and tested. The system consists of an atomizer that generates RAE particles and a four channel condensation particle counter (CPC). During the several months' operation in manufacturing line, the system was successfully tested and showed reliable results.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.415-420
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• 2001

Water usage in the semiconductor industries is dramatically increased by not only using bigger wafer from 8 inches to 12 inches but also by adapting new process such as Chemical Mechanical Planarization (CMP) process invented by IBM in late '80. However, The document published by International Semiconductor Association suggests the decreasing ultra pure water (UPW) use from 22 gallon/in$^2$in 1997 to 5 gallon/in$^2$ in 2012. The criteria will possibly used as exporting obstacle in the future. Generally, Solid content of CMP slurry is about 15wt%. The slurry is diluted with UPW before fed to a CMP process. When the slurry is discharged from the process as waste, it contains 0.1~0.6wt% of solid content and 9~10 at pH. The CMP waste slurry is discharged to stream with minimum treatment. In this study, to find optimum condition of coagulation for water recovery from the waste CMP slurry various condition of coagulation were examined. After coagulation far 0.1 wt% solid content of waste CMP slurry, the sludge volume was 10~15% after 30 min of sedimentation time. For the 0.5 wt%, sludge volume was 50~55% after one hour of sedimentation time. For more than 80% of water recycling, the solid content should be in the range of 0.1 to 0.2wr%. Based on the result of the turbidity removal, the Zeta Potential and the analysis of heavy metals, the optimum condition for 0.1 wr% of waste CMP slurry was with 20 mg/L of PACI at 4 to 5 of pH. The result showed that the optimum conditions fer the 0.1 wt% waste CMP slurry were 100mg/L of Alum at 4~5 of pH, 100 mg/L of MgCI$_2$at pH 10 to 11 and 100 mg/L of Ca(OH)$_2$at pH 9 to 11, respectively.

• Korean Journal of Ecology and Environment
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• v.53 no.2
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• pp.109-137
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• 2020

Upo Wetland is the largest riverine wetland in Korea which has been inscribed on the Ramsar List of Wetlands of International Importance in 1998. In this study, sedimentological study was carried out in order to understand the environmental changes in Upo Wetland during the Holocene. The drilling work for recovering the Quaternary sediments was conducted on the inner part (UPW17-01, UPW17-02, and UPW17-03) and the outer part (UPL17-01, UPL17-02) of the Upo Wetland. The recovered sediments are commonly characterized by gravel-dominated deposits in the lower part and silty clay-dominated deposits in the middle to upper parts respectively, which are seemed to be changed from fluvial to palustrine/lacustrine environments around 4,000 cal yr BP. In order to establish the Holocene diatoms distribution from Upo Wetland, we identified 63 diatom taxa. Of these, 14 species were new records for Korea: Gomphonema consector, Gomphonema jadwigiae, Hantzschia abundans, Luticola pseudomurrayi, Luticola spauldingiae, Neidium suboblongum, Ninastrelnikovia gibbosa, Oricymba rhynchocephala, Pinnularia borealis var. lanceolata, Pinnularia latarea, Pinnularia paliobducta, Pinnularia saprophila, Sellaphora laevissima, Stauroneis pseudoschimanskii. All identified diatom species are illustrated by high-quality scanning electron microscopic and light microscopic microphotographs. The ecological habitat for all taxa are presented.

• Clean Technology
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• v.7 no.3
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• pp.215-223
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• 2001

A present semiconductor cleaning technology is based upon RCA cleaning technology which consumes vast amounts of chemicals and ultra pure water(UPW) and is the high temperature process. Therefore, this technology gives rise to the many environmental issues, and some alternatives such as electrolyzed water(EW) are being studied. In this work, intentionally contaminated Si wafers were cleaned using the electrolyzed water. The electrolyzed water was generated by an electrolysis system which consists of three anode, cathode, and middle chambers. Oxidative water and reductive water were obtained in anode and cathode chambers, respectively. In case of NH4Cl electrolyte, the oxidation-reduction potential and pH for anode water(AW) and cathode water(CW) were measured to be +1050mV and 4.8, and -750mV and 10.0, respectively. AW and CW were deteriorated after electrolyzed, but maintained their characteristics for more than 40 minutes sufficiently enough for cleaning. Their deterioration was correlated with CO2 concentration changes dissolved from air. Contact angles of UPW, AW, and CW on DHF treated Si wafer surfaces were measured to be $65.9^{\circ}$, $66.5^{\circ}$ and $56.8^{\circ}$, respectively, which characterizes clearly the eletrolyzed water. To analyze the amount of metallic impurities on Si wafer surface, ICP-MS was introduced. It was known that AW was effective for Cu removal, while CW was more effective for Fe removal. To analyze the number of particles on Si wafer surfaces, Tencor 6220 were introduced. The particle distributions after various particle removal processes maintained the same pattern. In this work, RCA consumed about $9{\ell}$ chemicals, while EW did only $400m{\ell}$ HCl electrolyte or $600m{\ell}$ NH4Cl electrolyte. It was hence concluded that EW cleaning technology would be very effective for promoting environment, safety, and health(ESH) issues in the next generation semiconductor manufacturing.

• Journal of the Semiconductor & Display Technology
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• v.2 no.3
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• pp.1-6
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• 2003

In the rapid changes of the semiconductor manufacturing technologies for early 21st century, it may be safely said that a kernel of terms is the size increase of Si wafer and the size decrease of semiconductor devices. As the size of Si wafers increases and semiconductor device is miniaturized, the units of cleaning processes increase. A present cleaning technology is based upon RCA cleaning which consumes vast chemicals and ultra pure water (UPW) and is the high temperature process. Therefore, this technology gives rise to environmental issue. To resolve this matter, candidates of advanced cleaning processes have been studied. One of them is to apply the electrolyzed water. In this work, electrolyzed water cleaning was compared with various chemical cleaning, using Si wafer surfaces by changing cleaning temperature and cleaning time, and especially, concentrating upon the contact angle. It was observed that contact angle on surface treated with Electrolyzed water cleaning was $4.4^{\circ}$ without RCA cleaning. Amine series additive of high pKa (negative logarithm of the acidity constant) was used to observe the property changes of cathode water.

• Membrane and Water Treatment
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• v.5 no.2
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• pp.87-108
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• 2014

Electrodeionization (EDI), which combines electrodialysis (ED) and conventional ion-exchange (IX), is a mature process which has been applied since more than twenty years on commercial use for the production of ultrapure water (UPW). Eliminating chemical regeneration is the main reason for its commercial success. The increase in acceptance of EDI technology has led to an installation of very large plant as the commercial state of the art that produces $1,500m^3/h$ of water for high pressure steam boiler. More recently, EDI system has found a number of new interesting applications in wastewater treatment, biotechnology industry, and other potential field. Along with further growth and wider applications, the development of stack construction and configuration are also become a concern. In this paper, the principle of EDI process is described and its recent developments, commercial scale, and various applications are pointed out.

• Clean Technology
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• v.6 no.1
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• pp.79-84
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• 2000

In this study, to reduce the consumption of chemicals in cleaning processes, Si-wafers contaiminated with metallic impurities were cleaned with electrolyzed water(EW), which was generated by the electrolysis of a diluted electrolyte solution or ultra pure water(UPW). Electrolyzed water could be controlled for obtaining wide ranges of pH and ORP(oxidation-reduction potential). The pH and oxidation-reduction potential of anode water and cathode water were measured to be 4.7 and +1000mV, and 6.3 and -550mV, respectively. To analyze the amount of metallic impurities on Si-wafer surfaces, ICP-MS was introduced. Anode water was effective for Cu removal, while cathode water was more effective for Fe removal.