• ETRI Journal
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• v.35 no.4
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• pp.571-577
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• 2013

The fabrication of a thin-film transistor backplane and a liquid-crystal display using printing processes can eliminate the need for photolithography and offers the potential to reduce the manufacturing costs. In this study, we prepare contact via structures through a poly(methyl methacrylate) polymer insulator layer using inkjet printing. When droplets of silver ink composed of a polymer solvent are placed onto the polymer insulator and annealed at high temperatures, the silver ink penetrates the interior of the polymer and generates conducting paths between the top and bottom metal lines through the partial dissolution and swelling of the polymer. The electrical property of various contact via-hole interconnections is investigated using a semiconductor characterization system.

• Korean Journal of Materials Research
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• v.30 no.11
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• pp.573-580
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• 2020

YAG (Yttrium Aluminum Garnet, Y₃Al₅O₁₂) has excellent plasma resistance and recently has been used as an alternative to Y₂O₃ as a chamber coating material in the semiconductor process. However, due to the presence of an impurity phase and difficulties in synthesis and densification, many studies on YAG are being conducted. In this study, YAG powder is synthesized by an organic-inorganic complex solution synthesis method using PVA polymer. The PVA solution is added to the sol in which the metal nitrate salts are dissolved, and the precursor is calcined into a porous and soft YAG powder. By controlling the molecular weight and the amount of PVA polymer, the effect on the particle size and particle shape of the synthesized YAG powder is evaluated. The sintering behavior of the YAG powder compact according to PVA type and grinding time is studied through an examination of its microstructure. Single phase YAG is synthesized at relatively low temperature of 1,000 ℃ and can be pulverized to sub-micron size by ball milling. In addition, sintered YAG with a relative density of about 98 % is obtained by sintering at 1,650 ℃.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.158-161
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• 2003

The primary aim of this study is to investigate new semi-abrasive free slurry including acid colloidal silica and hydrogen peroxide for copper chemical-mechanical planarization (CMP). In general, slurry for copper CMP consists of colloidal silica as an abrasive, organic acid as a complex-forming agent, hydrogen peroxide as an oxidizing agent, a film forming agent, a pH control agent and several additives. We developed new semi-abrasive free slurry (SAFS) including below 0.5% acid colloidal silica. We evaluated additives as stabilizers for hydrogen peroxide as well as accelerators in tantalum nitride CMP process. We also estimated dispersion stability and Zeta potential of the acid colloidal silica with additives. The extent of enhancement in tantalum nitride CMP was verified through anelectrochemical test. This approach may be useful for the application of single and first step copper CMP slurry with one package system.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1293-1294
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• 2006

OLEDs based on organic thin films are similar to semiconductor base light-emitting diodes in that they were also considered to be one of the next generation flat-panel displays. They are attractive because of low-operating voltage, low power consumption, ease of fabrication, and low cost. In this study, we used poly (3,4-ethylenedioxythiophene)/poly (4-styrenesulfonate) (PE DOT : PSS) as a hole injection layer. In this experiment spin coating method was used with various speed rate. The fundamental structure of the OLEDs was ITO/PEDOT:PSS/NPB/$Alq_3$/Al. As a result, we obtained the enhancement performance of OLEDs when the spin coating speed was 4000 rpm. We obtained a maximum luminance of 24334 $cd/m^2$ at a current density of 967 $mA/cm^2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.78-78
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• 2007

In semiconductor devices, Cu has been used for the formation of multilevel metal interconnects by the damascene technique. Also lower dielectric constant materials is needed for the below 65 nm technology node. However, the low-k materials has porous structure and they can be easily damaged by high down pressure during conventional CMP. Also, Cu surface are vulnerable to have surface scratches by abrasive particles in CMP slurry. In order to overcome these technical difficulties in CMP, electro-chemical mechanical planarization (ECMP) has been introduced. ECMP uses abrasive free electrolyte, soft pad and low down-force. Especially, electrolyte is an important process factor in ECMP. The purpose of this study was to characterize KOH and $KNO_3$ based electrolytes on electro-chemical mechanical. planarization. Also, the effect of additives such as an organic acid and oxidizer on ECMP behavior was investigated. The removal rate and static etch rate were measured to evaluate the effect of electro chemical reaction.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.310-310
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• 2010

Electronic and photovoltaic characteristics of two sensitizers (TA-BTD-CA and TA-BTD-St-CA), composed of a different $\pi$-conjugation in the linker group, have been investigated by theoretical and experimental methods. The electronic structure, transition dipole moment and oscillator strengths of two sensitizers have been scrutinized by using density functional theory (DFT) and time-dependent DFT (TD-DFT) method. The LUMO level and the oscillator strength of TA-BTD-St-CA was higher than that of TA-BTD-CA, which may facilitate the electron injection process as well as increase the absorption coefficient. The relative efficiencies of the electron injection from the excited sensitizer to nanocrystalline TiO2 and SnO2 films have also been investigated by nanosecond transient absorption spectroscopy. The relative electron injection efficiency of TA-BTD-St-CA exhibited similar injection efficiency for two different semiconductors. However, in the case of TA-BTD-CA sensitizer, electron injection into SnO2 was approximately three times larger than that into TiO2. This enhancement of electron injection of TA-BTD-CA for the SnO2 is due to the increment of the driving force caused by positive shift of conduction band of semiconductor, which was also confirmed from the investigation for the photovoltaic characteristics according to the electrolyte additive, such as LiI additive.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.159-168
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• 2005

Dye-sensitized solar cells (DSCs) have been under investigation for the past decade due to their attractive features such as high energy conversion efficiency and low production costs. The basis for energy conversion is the injection of electrons from a photoexcited state of a dye sensitizer into the conduction band of the nanocrystalline $TiO_2$ semiconductor upon absorption of light. It is believed that the DSC is one of the most promising candidates for renewable energy sources. In this review, the development trends and perspectives of DSCs are investigated.

• Korean Journal of Materials Research
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• v.13 no.10
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• pp.673-676
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• 2003

We have investigated $Al_{x}$ $Ga_{l-x}$ N/GaN epilayers (x = 0.08, 0.15) grown by metal organic vapor phase epitaxy on sapphire with photoluminescence(PL), and persistent photoconductivity(PPC) experiments. An anomalous S-shaped shift behavior of temperature dependencies of PL peak energy is observed for the x = 0.15 sample. In PPC measurement, showed that the dark current recovery time of $Al_{x}$$Ga_{l-x}$ N/GaN epilayers mainly depends on the Al content. These behaviors are usually attributed to the presence of carrier localization states. All these phenomena are explained based on the alloy compositional fluctuations in the $Al_{x}$ /$Ga_{l-x}$ N/ epilayers. The photocurrent quenching observed in PPC measurements for $Al_{x}$ $Ga_{l-x}$ N/ epilayers less than 0.2 $\mu\textrm{m}$ thickness indicates that the presence of metastable state in the bandgap of GaN layer, and that the excess holes in the valence band recombine with free electrons.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.327-330
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• 2003

We present the fabrication and measured performance of a wavelength tunable Butt coupled DBR-LD. An average coupling efficiency between active layer and passive waveguide layer was measured over 85％per facet, and the average threshold current was 21 ㎃ for the waveguide integrated DBR laser. High output power of Butt coupled DBR-LD was obtained over 25 ㎽. As high as 25 ㎽ of output power was achieved by the butt coupled method. The maximum wavelength tuning range is about 7.4 nm, and the side mode suppression ratio was more than 40 ㏈ using 1.3 ${\mu}{\textrm}{m}$ InGaAsP waveguide layer.

• Korean Journal of Metals and Materials
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• v.48 no.4
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• pp.363-368
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• 2010

N,N'-diphenyl-N,N'-bis(3-methylphenyl)1-1' biphenyl-4,4'-diamine (TPD) hole-transporting layers were deposited using a continuous slot-die coating method on ITO/PET flexible substrates. It is crucial that the substrates have a very smooth surface with a RMS roughness of less than 2 nm for the deposition of semiconductor nanocrystals or Quantum Dots. The parameters of the slot-die coating, including the solution concentration of the TPD, the gap between the slot-die and the substrates, and the coating speed were controlled in these experiments. To obtain full coverage of the TPD films on the ITO/PET substrates (40 mm wide and several meters long), the injection rates of the TPD solution were increased proportional to the coating speed of the flexible substrates. Additionally, the injection rates must be increased as the gap distance changes from 400 to 600 ${\mu}m$ at the same coating speed. A RMS surface roughness of less than 2 nm was obtained, in contrast to bare ITO/PET substrates, at 13 nm, as the coating speed and gap distance increased.