• Particle and aerosol research
• /
• v.9 no.4
• /
• pp.261-269
• /
• 2013

The chemical mechanical polishing (CMP) process is widely used in semiconductor manufacturing process for planarization of various materials and structures. Point-of-use (POU) filters are used in most of the CMP processes in order to reduce the unwanted micro-scratches which may result in defects. The performance of the POU filter is depends on type and size of the abrasives used during cleaning process. For this reason, there is a need to evaluate POU filters for their filtration efficiency (FE) with different types of abrasives. In this study, we developed filter test system to evaluate the FE of POU using ceria and silica abrasives (slurry). The POU filter is roll type capsule filter with retention size of 0.2 ${\mu}m$. Two POU filters of different make are evaluated for FE. We observed that both POU filters show similar filtration efficiency for silica and ceria slurry. Results reveal that the ceria slurry and the colloidal silica particle are removed not only by mechanical way but also hydrodynamic and electrostatic interaction way.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.1
• /
• pp.13-20
• /
• 2010

Airborne particulate matters have two modes of size distributions of coarse mode and fine mode. The coarse mode which is formed by break down mechanism of large particles has a peak around the $100\;{\mu}m$, and the fine mode formed by condensation and build up mechanism of evaporated vapors has a peak at several ${\mu}m$. The coarse mode particles can be removed easily by conventional collecting equipments such as a cyclone, an electrostatic precipitator, and a filter, however the fine mode particles can not be collected easily. Usually the fine mode particles are generated in the high temperature conditions especially through boilers and incinerators, so the high efficient and temperature filter is essential for the filtration. In this study, a nano ceramic filter for the removal of fine particles in the high temperature is developed and tested for several characteristics. The nano ceramic filter has double layer of micro and nano structure and the pressure drop and the filtration efficiency for $0.31\;{\mu}m$ at 3 cm/s are 15.45 mmAq, and 96.75%, respectively. The thermal conductivity is $0.038\;W/m{\cdot}K$, and the coefficient of water vapor permeability is $3.63\;g/m^2{\cdot}h{\cdot}mmHg$. It is considered that the sensible heat exchange rate is very poor because the low thermal conductivity but it has high potential to exchange latent heat.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1997.06a
• /
• pp.207-231
• /
• 1997

The use household water purifier is continuously increasing due to the distrust of the piped, rap water, which may be caused by the deterioration of water quality and water supply facilities in Korea. The water purifier distributing in the domestic market is the membrane type that composes of membrane as a basic filter, sediment filter as a prefilter and activated carbon filter instead of one purifying water system. The membrane type using as a water cleaning system is mainly the method of micro filtration(NIF) as well as ultra filtration(UF) and reverse osmosis(RO). The types of MF and UF are using to remove suspended solids and virus, and RO is using to remove ionic compound in chemical organic compounds. At the beginning the household water purifier was imported as end-product or assembled by only importing module from small businesses in Korea. Therefore, people was hard to confide in the product quality because the sales policy and management of water purifier by small business were not effectively organized. However, the defects of water purifier having up to now ate improving by the efforts of special branches of water purifier and large enterprises, and new great products are developing and producing. To develop the best quality product of water purifier in Korea, it should be considered seasonal water characteristrics rather than any other condition. For example, the water purifier can be affected by the water temperature change, increase of suspended solids in the rainy season and inflow of raw water having concentration in a dry season. The subject we have to investigate in the future is to develop the water purifying system adaptable in Korea which can treat the water quality using close analyses of local and seasonal water characteristics.

• Analytical Science and Technology
• /
• v.20 no.2
• /
• pp.115-123
• /
• 2007

The heterocyclic amines (HAs) are a family of mutagenic/carcinogenic chemicals formed from the cooking of muscle meats such as beef, meat, fowl, and fish. A major draw back in the analysis of HAs from foods is their very low level of concentration (ng/g) and a number of matrix interferences in samples. Solid-phase extraction (SPE) is one of the procedures widely used for the extraction and purification of HAs in food samples. In this study, several SPE procedures of HAs determination were performed. Recoveries of the HAs were obtained from comparing a matrix such as a standard methanolic solution and pre-cooked meat extracts. Recovery values were ranging between 25.3 and 93.0 % at a concentration of 25.0 ng/g. HAs were determined with high sensitivity by micro-HPLC (${\mu}$-HPLC) analysis with electrospray ionization mass spectrometry (ESI-MS). Another developed method, which is freezing filtration method, shows better extraction recoveries and good precisions. The established method will be applicable to monitoring of heterocyclic amines from the cooked meat.

• Ecology and Resilient Infrastructure
• /
• v.3 no.4
• /
• pp.221-230
• /
• 2016

Multi-functional floating wetland island (mFWI) was developed in order to prevent algal bloom and to improve water quality through several unit purification processes. A test bed was applied in the stagnant watershed in an urban area, from the summer to the winter season. For the advanced treatment, an artificial phosphorus adsorption/filtration medium was applied with micro-bubble generation, as well as water plants for nutrient removal. It appeared that the efficiency of chemical oxygen demand (COD) and total phosphorus (T-P) removal was higher in the warmer season (40.9%, 45.7%) than in the winter (15.9%, 20.0%), and the removal performance (suspended solid, chlorophyll a) in each process differs according to seasonal variation; micro-bubble performed better (33.1%, 39.2%) in the summer, and the P adsorption/filtration and water plants performed better (76.5%, 59.5%) in the winter season. From the results, it was understood that the mFWI performance was dependent upon the pollutant loads in different seasons and unit processes, and thus it requires continuous monitoring under various conditions to evaluate the functions. In addition, micro-bubbles helped prevent the formation of anaerobic zones in the lower part of the floating wetland. This resulted in the water circulation to form a new healthy aquatic ecosystem in the surrounding environment, which confirmed the positive influence of mFWI.

• Journal of Korean Society on Water Environment
• /
• v.24 no.4
• /
• pp.423-429
• /
• 2008

Microfiltration (MF) and ultrafiltration (UF) processes for removal of particulate materials (i.e., turbidity, microorganisms and viruses) have been used to produce drinking water with higher quality. As membrane filtration technique has become widely applied for drinking water treatment, the importance of membrane integrity test (MIT) has also been increasingly emphasized. The results of pressure decay test (PDT) were presented in the paper to monitor membrane integrity. In this paper the PDT was carried out with deliberately-defected membrane fibers to evaluate the sensitivity of PDT on membrane fiber damage. Variation of pressure decay rate and removal rate were investigated to evaluate the impact of defection (defection ratio) and pore size of membrane. The membrane integrity could be successfully monitored by the PDT. The pressure decay rate varied from $0.002{\sim}0.189kg_f/cm^2hr$ with the initial pressure ranged from 0.2 to $1.0kg_f/cm^2hr$. Higher initial pressure which provided with higher pressure decay rate was preferred to evaluate the defection of membrane fiber. As for the particle removal rate, the Log Removal Rate (LRV) of kaolin solution decreased significantly from 3.78 to 2.31 when one fiber out of 3,200 fibers was cut. The membranes with different pore size were tested to evaluate virus removal efficiency. The virus removal rate of the MF membrane ($0.1{\mu}m$) was about 30% although the poliovirus was smaller than the pore size of the MF membrane, indicating that the removal rate was much lower than Korea Water Works Association (KWWA) certificate LRV of 1.5.

• Progress in Medical Physics
• /
• v.14 no.2
• /
• pp.81-89
• /
• 2003

The dose distributions of designed Ir-192 micro-source were investigated by dose computations which were accomplished by employing shape of encapsule material and thickness of the source for self-absorption. The computation dose derived from air-kerma rate (S$_{k}$ ) and dose rate constant (Λ) includes the anisotropy of dose distribution around the source. We got the dose rate constants in a water medium is 1.154 cGy h$^{-1}$ U$^{-1}$ . The size of the source was 0.5 mm in diameter and 3.5 mm in length and it was encapsuled in 1.1 mm$\Phi$${\times}$5.5 mm of stainless steel sealed with 0.3 mm of filter thickness. The tissue dose of reference point at 1.0 cm radial distance of the source axis was delivered 1.154 Uh$^{-1}$ (1.3167${\times}$10$^{-3}$ cGy/mCi-sec) from the S$_{k}$ 4.108U/mCi of Ir-192 source. The filtration effect contributed to air-kerma strength as exponential filtering effect of 86.2% in total attenuation, but self-absorption was 88.4% from radial dose distributions. In particular, the dose attenuations showed a rapid anisotropic distributions as 56% of reference dose along to $\pm$10 degrees from the tip of source axis and 50% for of that to source-cable direction. We persist in use the large diameter of applicator will avoid the dose anisotropy by the filtered attenuation effects along the axis of Ir-192 micro-source.

• Journal of Korean Society on Water Environment
• /
• v.24 no.6
• /
• pp.793-800
• /
• 2008

Recently domestic drinking water industry has recognized membrane-based technology as a promising alternative for water treatment. To ensure successful application of membrane processes, the integrity of membrane systems should be maintained. According to US EPA guidance, the pressure decay test based on the bubble point theory is recommended to detect any membrane defection of which size is close to the smallest diameter of Cryptosporidium oocysts, $3{\mu}m$. Proper implementation of the pressure decay test is greatly affected by initial test pressure, and the interpretation of the test results is associated with upper control limit. This study is conducted to investigate various factors affecting determination of initial test prtessure and upper control limit, including membrane-based parameters such as pore shape correction factor, surface tension and contact angle, and system-based parameters, such as volumetric concentration factor and total volume of system. In this paper, three different hollow fibers were used to perform the pressure decay test. With identical initial test pressure applied, their pressure decay tendency were different from each other. This finding can be explained by the micro-structure disparity of those membranes which is verified by FESEM images of those membranes. More specifically, FESEM images revealed that three hollow fibers have asymmetry, deep finger, shallow finger pore shape, respectively. In addition, sensitivity analysis was conducted on five parameters mentioned above to elucidate their relation to determination of initial test pressure and upper control limit. In case of initial pressure calculation, the pore shape correction factor has the highest value of sensitivity. For upper control limit determination, system factors have greater impact compared to membrane-based parameters.

• Proceedings of the KIEE Conference
• /
• 1999.07d
• /
• pp.1888-1890
• /
• 1999

In this work, we have systematically studied the effects of filtration and the defect trend as a function of polished wafer count using various filters in Inter-Metal Dielectric(IMD) CMP. The filter Installation in CMP polisher makes defect reduced after IMD CMP. As a result of formation micro-scratches, it shows that slurry filter plays an important role in determining consumable pad lifetime. The filter lifetime is dominated by the defects. We have acknowledged slurry filter lifetime is fixed by the degree of generating defects.

• Transactions of Materials Processing
• /
• v.14 no.5 s.77
• /
• pp.473-476
• /
• 2005

The demand of on-chip total analyzing system with MEMS (micro electro mechanical system) bio/chemical sensor is rapidly increasing. In on-chip total analyzing system, to detect the bio/chemical products with submicron feature size, a filtration system with nano-filter is required. One of the conventional methods to fabricate nano-filter is to use direct patterning or RIE (reactive ion etching). However, those procedures are very costly and are not suitable fur mass production. In this study, we suggested new fabrication method for a nano-filter based on replication process, which is simple and low cost process. After the Si master was fabricated by laser interference lithography and reactive ion etching process, the polymeric mold was replicated by UV-imprint process. Metallic nano-filter was fabricated after removing the polymeric part of metal deposited polymeric mold. Finally, our fabrication method was applied to metallic nano-filter with $1{\mu}m$ pitch size and $0.4{\mu}m$ hole size for bacteria sensor application.