• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.3
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• pp.319-325
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• 2017

Through silicon via (TSV) technology is extensively used in 3D IC integrations. The special structure of the TSV is realized by CMP (Chemically Mechanical Polishing) process with a high Cu removal rate and, low dishing, yielding fine topography without defects. In this study, we investigated the electrochemical behavior of copper slurries with various inhibitors in the Cu CMP process for advanced TSV applications. One of the slurries was carried out for the most promising process with a high removal rate (${\sim}18000{\AA}/Min$ @ 3 psi) and low dishing (${\sim}800{\AA}$), providing good microstructure. The effects of pH value and $H_2O_2$ concentration on the slurry corrosion potential and Cu static etching rate (SER) were also examined. The slurry formula with a pH of 6 and 2% $H_2O_2$, hadthe lowest SER (${\sim}75{\AA}/Min$) and was the best for TSV CMP. A novel Cu TSV CMP process was developed with two CMPs and an additional annealing step after some of the bulk Cu had been removed, effectively improving the condition of the TSV Cu surface and preventing the formation of crack defects by variations in wafer stress during TSV process integration.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.206-210
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• 2018

Two kinds of bioactive glass were coated on the Ti6Al4V alloy by the enameling technique. In order to reduce the thermal stress due to the difference in expansion coefficient with the alloy with the secondary coating forming hydroxyapatite, the difference in expansion coefficient between the alloy and the two glasses was adjusted at $2{\times}10^{-6}/^{\circ}C$ intervals. FE-SEM and EDS analysis showed that good adhesion was formed between the Ti6Al4V alloy and the primary coating by diffusion bonding. After immersion in SBF solution, it was confirmed from FT-IR that hydroxycarbonate apatite formed in the secondary coating was not different from bulk bioactive glass.

• The Korean Journal of Ecology
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• v.28 no.4
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• pp.231-235
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• 2005

Comparative water relations of Quercus acuta and Castanopsis cuspidata var, sieboldii were analyzed to assess their resistance to drought and low temperature stresses from early November to early December, As air temperature decreased both species showed an increased content of osmotically active solute concentration per unit of dry weight (NS/DW), leading to lower osmotic potential of both species at both full turgid state $(OP_{sat})$ and turgor loss point $(OP_{tlp})$ in December than November. No major difference in the ability to adjust osmotically was noticed between the two. This finding suggests that both species must respond adaptively under water and low temperature stresses to maintain turgor pressure in winter season. In addition to osmotic adjustment, a low bulk modulus of elasticity $(E_{max})$ shown in Castanopsis cuspidata var. sieboldii must also play an important role in turgor maintenance during winter season being apt to happen water and low temperature stresses in plants.

• The Journal of the Acoustical Society of Korea
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• v.23 no.5
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• pp.340-352
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• 2004

Acoustic streaming induced by the microscopic longitudinal ultrasonic vibration at 28.5 ㎑ is visualized between the quiescent glass plate and ultrasonic vibrator by particle imaging velocimetry(PIV) using laser. To investigate the augmentation of air flow velocity of acoustic streaming. the velocity variations of air streaming between the stationary plate and ultrasonic vibrator are measured in real-time. It is experimentally investigated that the magnitude of the acoustic streaming dependent upon the gap between the ultrasonic vibrator and stationary p1ate results in the variations of the average velocity fields as a outcome of the bulk air flow caused by the ultrasonic vibration. In addition. maximum acoustic streaming velocity exists at resonant gap. 18mm that is one of the resonant gaps (H=18, 24, 30, 36㎜) at which resonance occurs. The variation of the local maximum turbulent intensity with axial direction appear to reveal the value of 8%∼70% dependent upon the gap between the quiescent glass plate and ultrasonic vibrator. Shearstress is also maximized at the center region of the vibrator and the vorticity is also maximum and minimum in the neighborhood of the center of the vibrator at which the local maximum turbulent intensity and shear stress exist.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.45-50
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• 2005

During oxidation process, several type of defects are formed on the surface of the silicon crystal which was damaged mechanically before oxidation. As the size of abrasive particle increases multiple dislocation loops are produced favorably over oxidation-induced stacking faults, which are dominantly produced when ground with finer abrasive particle. These defects are not related with the crystal growth process like Czochralski or directional solidification. During directional solidification process, twins and stacking faults are the two major defects observed in the bulk of the silicon crystal. On the other hand, slip dislocations produced by the thermal stress are not observed. Thus, not only in single crystalline silicon crystal but also in multi-crystalline silicon, extrinsic gettering process with programmed production of surface defects might be highly applicable to silicon wafers for purification.

• Composites Research
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• v.23 no.4
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• pp.35-43
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• 2010

The purpose of this paper is to develop a Hybrid Fiber-reinforced High Strength Lightweight Cementitious Composite (HFSLCC) incorporated with lightweight filler and hybrid fibers for lightness and high ductility. Optimal ingredients and mixture proportion were determined on the basis of the micromechanical analysis and the steady-state cracking theory considering the fracture characteristics of matrix and the interfacial properties between fibers and matrix. Then 4 mixture proportions were determined according to the type and amount of fibers and the experiment was performed to evaluate the mechanical performance of those. The HFSLCC showed 3% of tensile strain, 4.2MPa of ultimate tensile stress, 57MPa of compressive strength and $1,660kg/m^3$ of bulk density. The mechanical performance of HFSLCC incorporated with PVA fibers of 1.0 Vol.% and PE fibers of 0.5 Vol.% is similar to those of the HFSLCC incorporated with fibers of 2.0 Vol.%.

• Journal of the Korean institute of surface engineering
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• v.32 no.2
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• pp.144-156
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• 1999

Thermal Barrier Coating with Functional Gradient Materials (FGM-TBC) can play an important role to protect the parts from harmful environments in high temperatures such as oxidation, corrosion, and wear and to improve the efficiency of aircraft engine by lowering the surface temperature on turbine blade. FGM-TBC can increase the life spans of product and improve the operating properties. Therfore, in this study the evaluations of mechanical and thermal properties of FGM-TBC such as fatigue, oxidation and wear-resistance at high temperatures have been conducted. The samples of both the TBC with 2, 3, 5 layers (YSZ/NiCrAlY) to be produced by Air Plasma Spray method (APS) and the bulk TBC with 6 layers to be produced by Plasma Assisted Sintering method (PAS) were used. Furthermore, residual stress, bond strength, and thermal conductivity were evaluated. The average thickness of the APS was 500$\mu\textrm{m}$ to 600$\mu\textrm{m}$ and the average thickness of the PAS was 3mm. The hardness number of the top layer of APS was 750 Hv to 810Hv and that of PAS was 950 Hv to 1440Hv. The $ZrO_2$ coating layer of APS was composed of tetragonal structure after spraying as the result of XRD analysis. As shown in the results of the high temperature wear test, the 3 layer coating of APS had the best wear resistance at $800^{\circ}C$ and the 5 layer coating of APS had the best wear resistance at $600^{\circ}C$. But, these coatings had the tendency of the low-temperature softening at $300^{\circ}C$. The main mechanism of wear was the adhesive wear and the friction coefficient of coatings was increased as increasing the test temperatures. A s results of thermal conductivity test, the ${\Delta}T$ of the APS coating was increased as number of layer and the range of thermal conductivity of the PAS was $800^{\circ}C$ to $1000^{\circ}C$.

• Korean Journal of Materials Research
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• v.11 no.5
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• pp.372-377
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• 2001

A theory developed in Part I has been applied to calculate effective elastic and thermoelastic moduli of particle-strengthened, unidirectionally fiber-reinforced, and layered composites. For the unidirectional fiber composites the effect of fiber aspect ratio is taken into account. The analytical solutions obtained to the effective elastic moduli are compared with some of existing expressions and the following results are found. The effective bulk and shear moduli of the particle strengthened composites coincide with Korner's expressions, which correspond with the lower bounds of Hanshin and Shtrikman. The same expressions as the lower bounds of Hill and Hanshin are obtained for five independent moduli of the aligned continuous fiber composites, four of which coincide with Hanshin and Rosen's exact solutions for 'composite cylinder assemblage'.

• Restorative Dentistry and Endodontics
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• v.28 no.2
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• pp.127-133
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• 2003

The object of this study was to compare the microleakage between various composite resin systems of multistep, one-bottle, and self-etching systems using electrical conductivity. After making class V cavities ($4{\times}3{\times}1.5{\;}mm$ around CEJ), they were bulk filled with three kinds of resins of A3. Teeth were storaged in a saline solution for one day, after then, they were finished and polished using Sof-Lex system. Another stress of thermocycling was made for 500 times from $5^{\circ}{\;}to{\;}55^{\circ}C$ with each dwelling time of 10 seconds. Electrical conductivity (microamphere, $\mu\textrm{A}$) was checked four times: before and after cavity preparation, after filing, after thermocycling. One-way ANOVA and 95% Scheffe Post Hoc test was used for checking any statistical difference among groups. Another 95% Paired Samples T-test was also used for estimating any significant difference within group after cavity filling or thermocycling. The results were as follows: 1 Every specimen showed various range of microleakage after filing. There was, however, no difference between composite resin systems. 2. All composite resin systems showed marked increase in microleakage with a thermocycling (p<0.05), there was, however, no difference between composite resin systems. 3. Although there was no significant difference between groups (p=0.078), one-bottle and self-etching systems seemed to be unstable than multistep system. Within the limits of this study, it was concluded that much more consideration should be needed when using thermally unstable one-bottle and self-etching systems that have multi-advantages from simplified step. More studies will be needed to solve these kinds of problems.

• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.415-422
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• 2014

Reinforced trackbeds are an important layer that has a significant effect on the deformation of the track, therefore, a deeper understanding of reinforced trackbeds is necessary. In this paper, we conduct a large triaxial test in order to evaluate the resilient modulus ($M_R$) of reinforced trackbed materials through considering several factors such as the grain size distribution (GSD) and loading conditions. It is identified that the maximum size of the particle, GSD, and compacted water content affect the $M_R$ but the loading frequency does not. Because these tests are performed with consideration of the field environment, the test results are useful for analyzing tracks including reinforced trackbeds. The data are limited to evaluating the parameters of $M_R$ model; however the parameters of the deviatoric and bulk stress models that can be used in various loading conditions are proposed.