• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.3
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• pp.205-212
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• 2002

The growth characteristics of metal-organic chemical vapor deposition (MOCVD) $Pb(Zr_xTi_{1-x})O_3 (PZT) thin films were investigated for the application of high-density ferroelectric random access memories (FRAM) devices beyond 64Mbit density. The supply control of Pb precursor plays the most critical role in order to achieve a reliable process for PZT thin film deposition. We have monitored the changes in the microstructure and electrical properties of films on increasing the Pb precursor supply into the reaction chamber. Under optimized conditions, $Ir/IrO_2/PZT(100nm)/Ir capacitor shows well-saturated hysteresis loops with a remanent polarization (Pr) of $~28{\mu}C/textrm{cm}^2$ and coercive voltage of 0.8V at 2.5V. Other issues such as step coverage, compositional uniformity and low temperature deposition was discussed in viewpoint of actual device application.

• Journal of the Semiconductor & Display Technology
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• v.8 no.4
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• pp.49-52
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• 2009

We have investigated the effect of the surface roughness of TCO substrate on the characteristics of OLED (organic light emitting diodes) devices. In order to control the surface roughness of ITO thin films, we have processed photolithography and reactive ion etching. The micro-size patterned mask was used, and the etching depth was controlled by changing etching time. The surface morphology of the ITO thin film was observed by FESEM and atomic force microscopy (AFM). And then, organic materials and cathode electrode were sequentially deposited on the ITO thin films. Device structure was ITO/$\alpha$-NPD/DPVB/Alq3/LiF/Al. The DPVB was used as a blue emitting material. The electrical characteristics such as current density vs. voltage and luminescence vs. voltage of OLED devices were measured by using spectrometer (minolta CS-1000A). The current vs. voltage and luminance vs. voltage characteristics were systematically degraded with increasing surface roughness. Furthermore, the retention test clearly presented that the reliability of OLED devices was directly influenced with the surface roughness, which could be interpreted in terms of the concentration of the electric field on the weak and thin organic layers caused by the poor step coverage.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.832-841
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• 2016

The voltage-frequency island (VFI) design paradigm has strong potential for achieving high energy efficiency in communication centric manycore system-on-chip (SoC) design called network-on-chip (NoC). However, because of the diminished scaling of wire-dimension and supply voltage as well as threshold voltage in modern CMOS technology, the vulnerability to link failure in VFI NoC is becoming a crucial challenge. In this paper, we propose an energy-optimized topology generation technique for VFI NoC to cope with permanent link failures. Based on the energy consumption model, we exploit the on-chip communication traffic patterns and characteristics of link failures in the early design stage to accommodate diverse applications and architectures. Experimental results using a number of multimedia application benchmarks show the effectiveness of the proposed three-step custom topology generation method in terms of energy consumption and latency without any degradation in the fault coverage metric.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.99-99
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• 2010

Recently, amorphous transparent oxide semiconductors (TOS) have been widely studied for many optoelectronic devices such as AM-OLED (active-matrix organic light emitting diodes). The TOS TFTs using a-IGZO channel layers exhibit a high electron mobility, a smooth surface, a uniform deposition at a large area, a high optical transparency, a low-temperature fabrication. In spite of many advantages of the sputtering process such as better step coverage, good uniformity over large area, small shadow effect and good adhesion, there are not enough researches about characteristics of a-IGZO thin films. In this study, therefore, we focused on the electrical properties of a-IGZO thin films as a channel layer of TFTs. TFTs with the a-IGZO channel layers and Y2O3 gate insulators were fabricated. Source and drain layers were deposited using ITO target. TFTs were deposited on unheated non-alkali glass substrates ($5cm{\times}5cm$) with a sintered ceramic IGZO disc (3 inch $\varnothing$, 5mm t), Y2O3 disc (3 inch $\varnothing$, 5mm t) and ITO disc (3 inch $\varnothing$, 5mm t) as a target by magnetron sputtering method. The O2 gas was used as the reactive gas. Deposition was carried out under various sputtering conditions to investigate the effect of sputtering process on the characteristics of a-IGZO thin films. Correlation between sputtering factors and electronic properties of the film will be discussed in detail.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.478.2-478.2
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• 2014

Atomic layer deposition (ALD) provides self-limiting processes based on chemisorption-based reactions. Such unique features allow for superior step coverage, atomic-scale control in thickness, and surface-dependent reaction controls. Furthermore, the surface-limited deposition enables the artificial deposition of oxide and/or metallic materials onto the porous systems as long as the supply is guaranteed in terms of time in providing reactant species and removing the byproducts and redundant reactants. The unique feature of atomic layer deposition is applied to solid oxide fuel cells whose incorporates two porous cathode and anode compartments in addition to the ionic electrolyte. Specific materials are deposited to the surface sites of porous electrodes, with the aim to controlling the triple phase boundaries crucial for the optimized SOFC performances. The effect of ALD on the SOFC performance is characterized using current-voltage characteristics in addition to frequency-dependent impedance spectroscopy. The pros and cons of ALD-controlled SOFCs are discussed toward high-performance SOFC systems.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.366.1-366.1
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• 2014

The rare-earth oxides M2O3 (M=La, Pr, Gd) are good insulators due to their large band gap (3.9eV for Pr2O3, 5.6eV for Gd2O3), they have high dielectric constants (Gd2O3 K=16, La2O3 K=27, Pr2O3 K=26-30) and, compared to ZrO2 and HfO2, they have higher thermodynamic stability on silicon making them very attractive materials for high-K dielectric applications. Another attractive feature of some rare-earth oxides is their relatively close lattice match to that of silicon, offering the possibility of epitaxial growth and eliminating problems related to grain boundaries in polycrystalline films. Metal-organic chemical vapor deposition (MOCVD) has been preferred to PVD methods because of the possibility of large area deposition, good composition control and excellent conformal step coverage. Herein we report on the synthesis of rare-earth oxide complexes with designed alkoxide and aminoalkoxide ligand. These novel complexes have been characterized by means of FT-IR, elemental analysis, and thermogravimetric analysis (TGA).

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.3
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• pp.299-305
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• 2020

Objectives: The most important occupational health activity is work environment measurement(WEM) along with the health examination. The preventive function of the WEM system could be achieved on the assumption that all subjected workplaces are performing correctly the WEM. To achieve properly the original purpose of WEM, we suggested a policy for subjected workplaces that they should register whether subjected or not. Methods: We made registration draft through reviewing laws, reports and thesis for WEM. And we conducted Focus Group Interview for industrial health experts using structured questionnaire about the registration. Results: There were 412 occupational deaths from 2013 to 2017. And it was found that only 130(31.6%) workplaces which involved in these occupational deaths had conducted the WEM. In order to operate the WEM system with effect, the subjected workplaces should register the subject status. Such registration must be completed at the stage of industrial accident insurance enrollment. Conclusions: Conducting WEM is the first step to prevent intoxication accident in workpalces. To operate properly WEM we should correctly understand subjected workplaces. So it is needed for all subjected workplaces to register whether they are subjected or not.

• Journal of the Korean Vacuum Society
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• v.11 no.3
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• pp.159-165
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• 2002

The physical properties of the TiN films deposited by ALD using $TiCl_4$and $NH_3$have been investigated. The TiN deposition rate is ~0.6 $\AA$ under an optimum deposition condition and the resistivity of the TiN films is 200~350 $\mu\Omega$cm . According to the XRD analysis results TiN films are crystallized in the ALD process window. AES analysis results show that the Cl impurity concentration in the TiN films is lower than 1 at% and that the atomic ratio of the TiN films is 1:1. Also it is found by SEM observation that the step coverage of the TiN films on which TiN films with trenches the aspect ratio of which is 10:1 is excellent.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.219-223
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• 2005

A promising capacitor, which has conformable step coverage and good uniformity of thickness and composition, is needed to manufacture high-density non-volatile FeRAM capacitors with a stacked cell structure. In this study, ferroelectric $Bi_{3.61}Nd_{0.39}Ti_3O_{12}$ (BNdT) thin films were prepared on $Pt(111)/TiO_2/SiO_2/Si$ substrates by the liquid delivery system MOCVD method. In these experiments, $Bi(ph)_{3}$, $Nd(TMHD)\_{3}$ and $Ti(O^iPr)_{2}(TMHD)_{2}$ were used as the precursors and were dissolved in n-butyl acetate. The BNdT thin films were deposited at a substrate temperature and reactor pressure of approximately $600^{\circ}C$ and 4.8 Torr, respectively. The microstructure of the layered perovskite phase was observed by XRD and SEM. The remanent polarization value (2Pr) of the BNdT thin film was $31.67\;{\mu}C/cm^{2}$ at an applied voltage of 5 V.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.2
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• pp.93-99
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• 2013

Fractal theory has been adopted as an effective tool for modelling complex and irregular natural phenomena facing in the fields of Computer Science, Engineering, Medical, Climatology and so on. In this paper, we presents an algorithm which enhances the performance of the triangular prism method(TPM) which has been widely used for fractal dimension extraction of natural terrains and images. For this, existing sampling methods are analyzed and a new sampling method which takes their merits is proposed. The effectiveness of the proposed algorithm is tested on fractal terrain maps and its performance is compared with that of other methods.