• 한국정밀공학회지
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• 제19권1호
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• pp.219-226
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• 2002

The mechanical etching technique has recently been developed to a powder blasting technique for various materials, capable of producing micro structures larger than 100$\mu$ m. This paper describes the performance of powder blasting technique in micro-pocketing of stainless steel and the effect of the number of nozzle scanning and the nozzle height on the depth and width of pockets. Experimental results showed that increasing the no. of nozzle scanning and decreasing the nozzle height resulted in the increase of depth and width in pockets. Increase of width results from wear of mask film.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.1269-1270
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• 2006

We investigated the effects of oxidizer additive on the performance of Cu-CMP process using commonly used tungsten slurry. According to the CMP removal rates and particle size distribution, and the micro-structures of surface layer as a function of oxidizer contents were greatly influenced by the slurry chemical composition of oxidizers. The difference in removal rate and roughness of copper surface are believed to cause by modification in the mechanical behavior of $Al_2O_3$ abrasive particles in CMP slurry.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1729-1730
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• 2006

We investigated the effects of oxidizer additive on the performance of Cu-CMP process using commonly used tungsten slurry. According to the CMP removal rates and particle size distribution, and the micro-structures of surface layer as a function of oxidizer contents were greatly influenced by the slurry chemical composition of oxidizers. The difference in removal rate and roughness of copper surface are believed to cause by modification in the mechanical behavior of $Al_{2}O_{3}$ abrasive particles in CMP slurry.

• 한국정밀공학회지
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• 제16권3호통권96호
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• pp.9-17
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• 1999

This paper presents a method of grinding and polishing automation of precision die after CNC machining. The method employs a robot system equipped with a pneumatic spindle and a special abrasive film pad. The robot program is automatically generated off-line program form a PC and downloaded to robot controller. Position and orientation data for the program is supplied form cutter contact (CC) data of NC machining process. This eliminates separate robot teaching process. This paper aims at practical automation of die finishing process which is very time consuming and suffering from shortage of workpeople. Time loss due to changeover from one product to another is eliminated by PC off-line programming exploiting appropriate NC machining data. Dextrous 6-axis robot with rigid wrist and simple tooling enables the process applicable to larger, rather complex 3 dimensional free surfaces.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2002년도 춘계학술발표회 초록집
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• pp.37-37
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• 2002

Diamoncl/Mo/Ni multi-layers on SKH-51 steel substrate was prepared to improve the abrasive wear resistance of a tool and die by a commercial chemical vapor deposition unit and electro-plating. The diamond after 7 hour deposition had cuba-octahedral structure with 2~5$\mu\textrm{m}$ grains. The existence of non-ferrous metals such as chromium, nickel and molybdenum between diamond and SKH-51 substrate results in forming higher quality of diamond layer by retarding carbon diffusion in the diamond layer during deposition, and also improving hardness and wear resistance. Surface cracks on the film was sometimes observed by the difference of by the thermal expansion coefficients between the steel substrate and the deposited layers during cooling.

• Tribology and Lubricants
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• 제35권6호
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• pp.389-395
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• 2019

In various industries, thin film coatings are used to improve friction and wear characteristics. Various types of tribotesters are used to evaluate the friction and wear characteristics of such thin film coatings. In this study, we fabricated a micro-tribotester and Tribo-scanning electron microscopy (SEM) to compare the friction and wear characteristics of copper (Cu) coatings under an atmospheric pressure and a vacuum condition, respectively. The reliability of the different types of tribotesters was evaluated by performing calibrations for the sensor to measure the friction forces and normal loads. Using the two different types of devices, the friction and wear tests are conducted at the same experimental conditions excluding environment conditions such as the atmospheric pressure and vacuum condition. The friction coefficient at the vacuum condition is lower than at the atmospheric pressure. This difference in friction characteristics is due to the fact that wear phenomena occur differently according to the atmospheric pressure and vacuum condition. At the atmospheric pressure, the abrasive wear is the main wear mechanism. At the vacuum condition, the adhesive wear is the main wear mechanism. The reason for the difference in the wear mechanism of the Cu coating at the atmospheric pressure and the vacuum condition is that the oxidation phenomenon, which does not appear at the vacuum condition, occurs at the atmospheric pressure; therefore, the characteristics of the Cu coating change accordingly.

• Tribology and Lubricants
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• 제32권4호
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• pp.119-124
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• 2016

In the sapphire wafering process, lapping is a crucial operation in order to reduce the damaged layer and achieve the target thickness. Many parameters, such as pressure, velocity, abrasive, slurry and plate, affect lapping characteristics. This paper presents an experimental investigation on the effect of the plate groove on the material removal rate and roughness of the wafer. We select the spiral pattern and rectangular type as the groove shapes. We vary the groove density by controlling the groove shape dimension, i.e., the groove width and pitch. As the groove density increases to 0.4, the material removal rate increases and gradually reaches a saturation point. When the groove density is low, the pressing load is mostly supported by the thick film, and only a small amount acts on the abrasives resulting to a low material removal rate. The roughness decreases on increasing the groove density up to 0.3 because thick film makes partial participations of large abrasives which make deep scratches. From these results, we could conclude that the groove affects the contact condition between the wafer and plate. At the same groove density, the pitch has more influence on reducing the film thickness than the groove width. By decreasing the groove density with a smaller pitch and larger groove width, we could achieve a high material removal rate and low roughness. These results would be helpful in understanding the groove effects and determining the appropriate groove design.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.545-545
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• 2008

Poly-Si is an essential material for floating gate in NAND Flash memory. To fabricate this material within region of floating gate, chemical mechanical polishing (CMP) is commonly used process for manufacturing NAND flash memory. We use colloidal silica abrasive with alkaline agent, polymeric additive and organic surfactant to obtain high Poly-Si to SiO2 film selectivity and reduce surface defect in Poly-Si CMP. We already studied about the effects of alkaline agent and polymeric additive. But the effect of organic surfactant in Poly-Si CMP is not clearly defined. So we will examine the function of organic surfactant in Poly-Si CMP with concentration separation test. We expect that surface roughness will be improved with the addition of organic surfactant as the case of wafering CMP. Poly-Si wafer are deposited by low pressure chemical vapor deposition (LPCVD) and oxide film are prepared by the method of plasma-enhanced tetra ethyl ortho silicate (PETEOS). The polishing test will be performed by a Strasbaugh 6EC polisher with an IC1000/Suba IV stacked pad and the pad will be conditioned by ex situ diamond disk. And the thickness difference of wafer between before and after polishing test will be measured by Ellipsometer and Nanospec. The roughness of Poly-Si film will be analyzed by atomic force microscope.

• Tribology and Lubricants
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• 제31권2호
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• pp.69-77
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• 2015

Recently, there have been reports of severe symptoms of wear in bearings due to foreign substances mixed in lubricants. Therefore, studying the effects of foreign substances (such as combustion products and metallic debris) on the wear characteristics of journal bearings and proposing appropriate management standards for lubricant cleanliness have become necessary. Studies on the effect of particle size and concentration of foreign substances on surface damage have actively progressed in the recent times. These studies indicate the possibility of foreign substances causing direct wear of bearing surfaces. However, experiments conducted until now involve only basic tests such as the Pin-on-Disk test instead of those involving real bearing systems. This study experimentally examines the damage to the surface of a journal bearing due to foreign substances (combustion products and alumina) mixed with the lubricant, as well as the effect of the type and size of particles on its wear characteristics. The study uses an experimental journal bearing similar to a real bearing system for conducting the lubrication test. Hydrodynamic Lubrication (HL) numerical analysis, experiment results, and film parameters are used for calculating the operating conditions required for achieving the desired film thickness, and the results of the analysis are modified for considering the surface roughness. The run-time of the experiment is 10 min including the stabilization process. The experiment results show that alumina particles larger than the minimum film thickness cause significant surface damage.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.34.2-34.2
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• 2011

The demand for Ru has been increasing in the electronic, chemical and semiconductor industry. Chemical mechanical planarization (CMP) is one of the fabrication processes for electrode formation and barrier layer removal. The abrasive particles can be easily contaminated on the top surface during the CMP process. This can induce adverse effects on subsequent patterning and film deposition processes. In this study, a post Ru CMP cleaning solution was formulated by using sodium periodate as an etchant and citric acid to modify the zeta potential of alumina particles and Ru surfaces. Ru film (150 nm thickness) was deposited on tetraethylorthosilicate (TEOS) films by the atomic layer deposition method. Ru wafers were cut into $2.0{\times}2.0$ cm pieces for the surface analysis and used for estimating PRE. A laser zeta potential analyzer (LEZA-600, Otsuka Electronics Co., Japan) was used to obtain the zeta potentials of alumina particles and the Ru surface. A contact angle analyzer (Phoenix 300, SEO, Korea) was used to measure the contact angle of the Ru surface. The adhesion force between an alumina particle and Ru wafer surface was measured by an atomic force microscope (AFM, XE-100, Park Systems, Korea). In a solution with citric acid, the zeta potential of the alumina surface was changed to a negative value due to the adsorption of negative citrate ions. However, the hydrous Ru oxide, which has positive surface charge, could be formed on Ru surface in citric acid solution at pH 6 and 8. At pH 6 and 8, relatively low particle removal efficiency was observed in citric acid solution due to the attractive force between the Ru surface and particles. At pH 10, the lowest adhesion force and highest cleaning efficiency were measured due to the repulsive force between the contaminated alumina particle and the Ru surface. The highest PRE was achieved in citric acid solution with NaIO4 below 0.01 M at pH 10.