• Korean Journal of Materials Research
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• v.18 no.3
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• pp.117-122
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• 2008

Micro-sized bumps on a multi-layered build-up PCB were fabricated by pulse-reverse copper electroplating. The values of the current density and brightener content for the electroplating were optimized for suitable performance with maximum efficiency. The micro-bumps thus electroplated were characterized using a range of analytical tools that included an optical microscope, a scanning electron microscope, an atomic force microscope and a hydraulic bulge tester. The optical microscope and scanning electron microscope analyses results showed that the uniformity of the electroplating was viable in the current density range of $2-4\;A/dm^2$; however, the uniformity was slightly degraded as the current density increased. To study the effect of the brightener concentration, the concentration was varied from zero to 1.2 ml/L. The optimum concentration for micro-bump electroplating was found to be 0.6 ml/L based on an examination of the electroplating properties, including the roughness, yield strength and grain size.

• Journal of the Korean Ceramic Society
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• v.28 no.8
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• pp.585-592
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• 1991

ZnO films were deposited onto Corning glass 7059 substrate in the temperature range from $200^{\circ}C$ to $450^{\circ}C$ by chemical vapor deposition technique using the hydrolysis of Diet ylzinc (DEZ). As the deposition temperature increased from $200^{\circ}C$ to $350^{\circ}C$, the deposition rate increased with the apparent activation energy of ∼23kJ/mole. Further increase of the deposition temperature above $400^{\circ}C$, however, resulted in a reduction of the rate. It was found that ZnO film grew with a strong C-axis preferred orientation at the temperature of $400^{\circ}C$. As the deposition temperature increased, the film resistivity decreased down to ∼0.2 $\Omega$cm at $450^{\circ}C$. The electrical resistivity was governed more likely by electron concentration rather than by electron mobility. Average optical transmission of the films in the optical wavelength range of 400 nm to 900 nm was over 90% and the optical energy band gap of 3.28∼3.32 eV was obtained from the direct transition.

• Journal of Astronomy and Space Sciences
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• v.33 no.1
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• pp.29-36
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• 2016

The East African ionosphere (3°S-18°N, 32°E-50°E) was mapped using Total Electron Content (TEC) measurements from ground-based GPS receivers situated at Asmara, Mekelle, Bahir Dar, Robe, Arbaminch, and Nairobi. Assuming a thin shell ionosphere at 350 km altitude, we project the Ionospheric Pierce Point (IPP) of a slant TEC measurement with an elevation angle of >10° to its corresponding location on the map. We then infer the estimated values at any point of interest from the vertical TEC values at the projected locations by means of interpolation. The total number of projected IPPs is in the range of 24-66 at any one time. Since the distribution of the projected IPPs is irregularly spaced, we have used an inverse distance weighted interpolation method to obtain a spatial grid resolution of 1°×1° latitude and longitude, respectively. The TEC maps were generated for the year 2008, with a 2 hr temporal resolution. We note that TEC varies diurnally, with a peak in the late afternoon (at 1700 LT), due to the equatorial ionospheric anomaly. We have observed higher TEC values at low latitudes in both hemispheres compared to the magnetic equatorial region, capturing the ionospheric distribution of the equatorial anomaly. We have also confirmed the equatorial seasonal variation in the ionosphere, characterized by minimum TEC values during the solstices and maximum values during the equinoxes. We evaluate the reliability of the map, demonstrating a mean error (difference between the measured and interpolated values) range of 0.04-0.2 TECU (Total Electron Content Unit). As more measured TEC values become available in this region, the TEC map will be more reliable, thereby allowing us to study in detail the equatorial ionosphere of the African sector, where ionospheric measurements are currently very few.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.220-220
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• 2011

The Ne-Xe plasmas in dense plasma-focus device with coaxial electrodes were generated for extreme ultraviolet (EUV) lithography. The influence of gas mixture ratio, Ne-Xe (1, 10, 15, 20, 25, 30, 50%) mixture gas, on EUV emission measurement, EUV intensity and electron temperature in the coaxially focused plasma were investigated. An input voltage of 4.5 kV was applied to the capacitor bank of 1.53mF and the diode chamber was filled with Ne-Xe mixture gas at a prescribed pressure. The inner surface of the cylindrical cathode was lined by an acetal insulator. The anode was made of tin metal. The EUV emission signal of the wavelength in the range of 6~16 nm has been detected by a photo-detector (AXUV-100 Zr/C, IRD). The visible emission line was also detected by the composite-grating spectrometer of the working wavelength range of 200~1100 nm (HR 4000CG). The electron temperature is obtained by the optical emission spectroscopy (OES) and measured by the Boltzmann plot with the assumption of local thermodynamic equilibrium (LTE).

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.332-332
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• 2011

The extreme ultraviolet (EUV) radiation, whose wavelength is from 120 nm down to 10 nm, and the energy from 10 eV up to 124 eV, is widely utilized such as in photoelectron spectroscopy, solar imaging, especially in lithography and soft x-ray microscopy. In this study, we have investigated the plasma diagnostics as well as the debris characteristics between the two types of dense plasma focusing devices with coaxial electrodes of Mather and hypocycloidal pinch (HCP), respectively. The EUV emission intensity, electron temperature and plasma density have been investigated in these cylindrical focused plasma along with the debris characteristics. An input voltage of 5 kV has been applied to the capacitor bank of 1.53 uF and the diode chamber has been filled with Ar gas at pressure ranged from 1 mTorr and 180 mTorr. The inner surface of the cathode was covered by polyacetal insulator. The central anode electrode has been made of tin. The wavelength of the EUV emission has been measured to be in the range of 6~16 nm by a photo-detector (AXUV-100 Zr/C, IRD). The visible emission has also been measured by the spectrometer with the wavelength range of 200~1,100 nm. The electron temperature and plasma density have been measured by the Boltzmann plot and Stark broadening methods, respectively, under the assumption of local thermodynamic equilibrium (LTE).

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.475-481
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• 2013

By using ionic liquid 1-hexylpyridinium hexafluorophosphate ($HPPF_6$) based carbon ionic liquid electrode (CILE) as the substrate electrode, a $CoMoO_4$ nanorods and myoglobin (Mb) composite was casted on the surface of CILE with chitosan (CTS) as the film forming material to obtain the modified electrode (CTS/$CoMoO_4$-Mb/CILE). Spectroscopic results indicated that Mb retained its native structures without any conformational changes after mixed with $CoMoO_4$ nanorods and CTS. Electrochemical behaviors of Mb on the electrode were carefully investigated by cyclic voltammetry with a pair of well-defined redox peaks from the heme Fe(III)/Fe(II) redox center of Mb appeared, which indicated that direct electron transfer between Mb and CILE was realized. Electrochemical parameters such as the electron transfer number (n), charge transfer coefficient (${\alpha}$) and electron transfer rate constant ($k_s$) were estimated by cyclic voltammetry with the results as 1.09, 0.53 and 1.16 $s^{-1}$, respectively. The Mb modified electrode showed good electrocatalytic ability toward the reduction of trichloroacetic acid in the concentration range from 0.1 to 32.0 mmol $L^{-1}$ with the detection limit as 0.036 mmol $L^{-1}$ ($3{\sigma}$), and the reduction of $H_2O_2$ in the concentration range from 0.12 to 397.0 ${\mu}mol\;L^{-1}$ with the detection limit as 0.0426 ${\mu}mol\;L^{-1}$ ($3{\sigma}$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.103-107
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• 2000

Boron Phosphide films were deposited on the glass substrate at the low temperature, 55$0^{\circ}C$, by the reaction of B$_2$H$_{6}$ with PH$_3$ using CVD. $N_2$ was employed as carrier gas. The optimal gas rates were 50 $m\ell$/min for B$_2$H$_{6}$, 50 $m\ell$/min for PH$_3$ $m\ell$/min and 1.5 $\ell$/min for $N_2$. To investigate the annealing effect, the films were annealed for 1hour, 3hours in $N_2$ambient at 55$0^{\circ}C$ and tested. The deposition rate was 1000$\AA$/min and the refractive index of film was 2.6. The measurement of X-RD shows that the films have the preferred orientation of (1 0 1) and the intensity of the peak for (1 0 1) orientation decreases according to the annealing time. The data of VIS spectrophotometer proved that the films are transparent in the visible range and the maximal transmittance increases according to the annealing time; 75.49% for as-deposited, 76.71% for 1hr-annealed and 86.4 % for 3hrs-annealed. The measurement of AFM shows that the average surface roughness increases according to the annealing time; 73$\AA$ for as-deposited, 88.9$\AA$ for 1hr-annealed and 220$\AA$ for 3hrs-annealed. Also, The data of the secondary electron emission rate(Υ) shows that the secondary electron emission rate increases according to the annealing time; 0.317 for 1hr-deposited, 0.357 for 1hr-annealed and 0.537 for 3hrs-annealed. And, The measurement of FT-IR that the characteristic of transmittance in the infrared range was stabilized through annealing.ing.

• Corrosion Science and Technology
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• v.20 no.5
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• pp.289-294
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• 2021

In this study, after measuring polarization characteristics of 97.3 wt% Ag, Au-Coated 97.3 wt% Ag (ACA) and 100 wt% Au wires in 1 wt% H₂SO₄ and 1 wt% HCl electrolytes at 25 ℃, corrosion rate and corrosion characteristics were comparatively analyzed. Comparing corrosion potential (E_CORR) values in sulfuric acid solution, ACA wire had more than six times higher E_CORR value than Au wire. Thus, it seems possible to use a broad applied voltage range of bonding wire for semiconductor packaging which ACA wire could be substituted for the Au wire. However, since the E_CORR value of ACA wire was three times lower than that of the Au wire in a hydrochloric acid solution, it was judged that the use range of the applied voltage and current of the bonding wire should be considered. In hydrochloric acid solution, 97.3 wt% Ag wire showed the highest corrosion rate, while ACA and Au showed similar corrosion rates. Additionally, in the case of sulfuric acid solution, all three types showed lower corrosion rates than those under the hydrochloric acid solution environment. The corrosion rate was higher in the order of 97.3 wt% Ag > ACA > 100 wt% Au wires.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.56-63
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• 2023

In this paper, we studied the effect of electron beam irradiation on sol-gel indium-gallium-zinc oxide (IGZO) thin films under air and nitrogen atmosphere and carried out the electrical characterization of the s ol-gel IGZO thin film transistors (TFTs). To investigate the optical properties, crystalline structure and chemical state of the sol-gel IGZO thin films after electron beam irradiation, UV-Visible spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were carried out. The sol-gel IGZO thin films exhibited over 80% transmittance in the visible range. The XRD analysis confirmed the amorphous nature of the sol-gel IGZO films regardless of electron beam irradiation. When electron beam irradiation was conducted in a nitrogen (N₂) atmosphere, we observed an increased proportion of peaks related to M-O bonding contributed to the improved quality of the thin films. Sol-gel IGZO TFTs subjected to electron beam exposure in a nitrogen atmosphere exhibited enhanced electrical characteristics in terms of on/off ratio and electron mobility. In addition, the electrical parameters of the transistor (on/off ratio, threshold voltage, electron mobility, subthreshold swing) remained relatively stable over time, indicating that the electron beam exposure process in a nitrogen atmosphere could enhance the reliability of IGZO-based thin-film transistors in the fabrication of sol-gel processed TFTs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.980-986
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• 2013

In this paper, the discharge characteristics of ac-type cylindrical discharge devices with diameters (D) in the $50{\sim}400{\mu}m$ range have been investigated numerically. The cylindrical devices have much lower breakdown voltages compared to the coplanar electrode structures. The breakdown voltage of the cylindrical structures increases with the decrease of diameters in $50{\sim}100{\mu}m$ range. In $100{\sim}200{\mu}m$ range, however, the breakdown voltage decreases slightly with the decrease of diameters. Also, as the diameter gets smaller, the electron heating efficiency is greatly improved.