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Three-dimensional Modeling for the Transmittance of ITO/Mesh-Ag/ITO Multilayers using FDTD
Eou-Sik Cho,Sang Jik Kwon 대한전자공학회 2021 Journal of semiconductor technology and science Vol.21 No.5
In order to improve the transmittance of ITO/Ag/ITO multilayers, Ag layer was formed with mesh structure. For more accurate and practical analysis, we performed the simulations using an optical wave simulator termed the full-wave simulation program. In our simulations, the three dimensional (3D) finite-difference time-domain (FDTD) method was used to realize the high density mesh structure, and a plane wave with variable wavelengths ranging from 250 to 850 nm is incident in the z-direction at normal incidence to the ITO/Mesh- Ag/ITO film surrounded by free-air space. From the simulation results, at a higher open ratio and lower Ag thickness, the transmittance of ITO/Mesh-Ag/ITO were not influenced by other parameters. Experimental measurements were performed depending on the various Ag mesh-spaces and mesh-widths. The open ratio of about 60 % has shown the acceptable results in the points of both the optical transmittance and the electrical conductance.
Novel Process Technologies of a Deep-submicron MOSFET for the High Packing Density of Circuits
Eou-Sik Cho,Sang Jik Kwon 대한전자공학회 2021 Journal of semiconductor technology and science Vol.21 No.6
We have presented some novel process ideas to solve the major challenging problems in submicron device techniques. The key ideas are the ultra-shallow LDD (lightly doped source/drain) junction formation by using the SPD (solid phase diffusion) through ‘amorphous Si / thin oxide’ layer and the Ti silicidation by using selectively etched a-Si layer which is extended over the field oxide region. This TiSi₂ layer could be used as a local interconnect with the shrinkage of physical design width of the active mask. Using this FESD (Field Extended Source Drain) technology, the width of the physical active mask could be reduced 2.75 times smaller than that of the conventional structure. We have verified this technology successfully by the fabrication of PMOSFET with 0.76 μm gate length.
Cho, Eou Sik,Kwon, Sang Jik The Korean Institute of Electrical and Electronic 2013 Transactions on Electrical and Electronic Material Vol.14 No.1
A volcano shaped gated Si-FEA (silicon field emitter array) was simply fabricated using sputtering as a gate electrode deposition and lift-off for the removal of the oxide mask, respectively. Due to the limited step coverage of well-controlled sputtering and the high aspect ratio in Si dry etch caused by high RF power, it was possible to obtain Si FEAs with a stable volcano shaped gate structure and to realize the restriction of gate leakage current in field emission characteristics. For 100 tip arrays and 625 tip arrays, gate leakage currents were restricted to less than 1% of the anode current in spite of the volcano-shaped gate structure. It was also possible to keep the emitters stable without any failure between the Si cathode and gate electrode in field emission for a long time.
Cho, Eou Sik,Kwon, Sang Jik The Korean Institute of Electrical and Electronic 2013 Transactions on Electrical and Electronic Material Vol.14 No.1
Frequency filters with various filtering wavelengths were used in the photoelectric characterization of hydrogenated amorphous silicon thin film transistor (a-Si:H TFT) and the experimental results were described and analyzed in terms of the photon energy spectral characteristics calculated from the integration of the photon energy and the spectral intensity of transmitted backlight through the filters at each wavelength. From the comparison of the photocurrents and the calculated photon energy spectrums for the filtered ranges of wavelength, it was possible to conclude that the photocurrents are closely related to the photon energy spectrums of the backlight.
OLED의 Thin Film Encapsulation을 위한 MgO 박막의 원자층 증착 장치 및 공정에 관한 연구
조의식,권상직,Cho, Eou Sik,Kwon, Sang Jik 한국반도체디스플레이기술학회 2021 반도체디스플레이기술학회지 Vol.20 No.3
Thin-film encapsulation (TFE) technology is most effective in preventing water vapor and oxygen permeation in the organic light emitting diodes (OLED). Of those, a laminated structure of Al<sub>2</sub>O<sub>3</sub> and MgO were applied to provide efficient barrier performance for increasing the stability of devices in air. Atomic layer deposition (ALD) method is known as the most promising technology for making the laminated Al<sub>2</sub>O<sub>3</sub>/MgO and is used to realize a thin film encapsulation technology in organic light-emitting diodes. Atomic layer deposited inorganic films have superior barrier performance and have advantages of excellent uniformity over large scales at relatively low deposition temperatures. In this study, the control system of the MgCP<sub>2</sub> precursor for the atomic layer deposition of MgO was established in order to deposit the MgO layer stably by the injection time of second level and the stable heating temperature. The deposition rate was obtained stably to be from 4 to 10 Å/cycle using the injection pulse times ranging from 3 to 12 sec and a substrate temperature ranging from 80 to 150 ℃.
Effect of the Ag thickness on the Light Extraction Efficiency of the OLED with an ITO/Ag/ITO Anode
Yongmin Jeon,Eou-Sik Cho,Sang Jik Kwon 대한전자공학회 2022 Journal of semiconductor technology and science Vol.22 No.5
The light extraction efficiency of the organic light emitting diodes (OLEDs) with an ITO/Ag/ITO anode was analyzed by using the finite-difference time domain (FDTD) simulation method. For different inserted Ag thickness, the light extraction ratio was reduced as increasing the Ag thickness. The simulation results also showed the light extraction ratio began to be saturated at a critical angle as increasing the simulation monitor num as a result of the extraction loss due to the wave-guide mode by a total internal reflection. From the simulated electric field profiles, the light-outcoupling loss due to the surface plasmon polariton (SPP) mode was more apparently investigated as increasing the Ag thickness. In the fabrication of the OLED with ITO/Ag/ITO anode, the Ag thickness should be optimized with respect to the light extraction efficiency of the OLED as well as the electrical conductivity of the anode.
A Study on the Band Structure of ZnO/CdS Heterojunction for CIGS Solar-Cell Application
Sim, Hana,Lee, Jeongmin,Cho, Seongjae,Cho, Eou-Sik,Kwon, Sang Jik The Institute of Electronics and Information Engin 2015 Journal of semiconductor technology and science Vol.15 No.2
In this paper, ZnO films were prepared by atomic layer deposition (ALD) and CdS films were deposited using chemical bath deposition (CBD) to form ZnO/CdS heterojunction. More accurate mapping of band arrangement of the ZnO/CdS heterojunction has been performed by analyzing its electrical and optical characteristics in depth by various methods including transmittance, x-ray photoemission spectroscopy (XPS), and ultraviolet photoemission spectroscopy (UPS). The optical bandgap energies ($E_g$) of ZnO and CdS were 3.27 eV and 2.34 eV, respectively. UPS was capable of extracting the ionization potential energies (IPEs) of the materials, which turned out to be 8.69 eV and 7.30 eV, respectively. The electron affinity (EA) values of ZnO and CdS calculated from IPE and $E_g$ were 5.42 eV and 4.96 eV, respectively. Energy-band structures of the heterojunction could be accurately drawn from these parameters taking the conduction band offset (CBO) into account, which will substantially help acquisition of the full band structures of the thin films in the CIGS solar-cell device and contribute to the optimal device designs.
Ahn, Min-Hyung,Cho, Eou-Sik,Kwon, Sang-Jik The Korean Infomation Display Society 2008 Journal of information display Vol.9 No.4
A DC-magnetron inline sputter was established, and the influence of the base pressure on the structural characteristics of the ITO thin films was studied. When the inline sputter system was established and operated for ITO sputtering, its initial vacuum level did not go below $5\times10^{-6}$ torr. The vacuum leak test was conducted by measuring t he elapsed time until the vacuum level reached $1\times10^{-6}$ torr. The base pressure was successfully maintained at $1\times10^{-6}$ torr for 900 min, and the uniformity of the ITO film that had been deposited at this pressure significantly improved.