• Journal of Information Display
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• v.11 no.3
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• pp.109-112
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• 2010

The solid phase compositions and dielectric properties of silicon nitride ($SiN_x$) films prepared using the plasma enhanced chemical vapor deposition (PECVD) technique at a low temperature ($200^{\circ}C$) were studied. Controlling the source gas mixing ratio, R = $[N_2]/[SiH_4]$, and the plasma power successfully produced both silicon-rich and nitrogen-rich compositions in the final films. The composition parameter, X, varied from 0.83 to 1.62. Depending on the film composition, the dielectric properties of the $SiN_x$ films also varied substantially. Silicon-rich silicon nitride (SRSN) films were obtained at a low plasma power and a low R. The photoluminescence (PL) spectra of these films revealed the existence of nano-sized silicon particles even in the absence of a post-annealing process. Nitrogen-rich silicon nitride (NRSN) films were obtained at a high plasma power and a high R. These films showed a fairly high dielectric constant ($\kappa$ = 7.1) and a suppressed hysteresis window in their capacitance-voltage (C-V) characteristics.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.11
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• pp.555-561
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• 2001

In this paper, the low power (1.5 W) solenoid-type magnetic thin-film transformers utilizing a $Ni_{81}Fe_{19)$ core material were designed and fabricated for 5 MHz-drive DC-DC converter application. The $20\mum$ thick copper films were used as the coils. The transformers fabricated in this work have the sizes of $3.08 mm\times25.5 mm\; and\; 6.15 mm\times12.75 mm.$ The optimum design of solenoid-type magnetic thin film transformers was performed utilizing the conventional equations, a Maxwell computer simulator (Ansoft HFSS V7.0 for PC), and parameters obtained from the magnetic properties of NiFe magnetic core materials. frequency characteristics of inductance, dc resistance (R), coupling factor (k) and gain of developed transformers were measured using HP4194A impedance and gain-phase analyzer. The fabricated transformers with the size of $6.15 mm\time12.75 mm$ exhibit the inductance of $0.83 \muH$, the dc resistance of $2.3\Omega$$\Omega$, the k of 0.91 and the gain of -1 dB at 5 MHz, which show the comparable results to those reported in the recent literatures. The measured high-frequency characteristics for the fabricated transformers agreed well with those obtained by theoretical calculations .

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.160-163
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• 2003

This paper describes on anodic bonding characteristics of MLCA(Multi Layer Ceramic Actuator) to Si-wafer using evaporated Pyrex #7740 glass thin-films for MEMS applications. Pyrex #7740 glass thin-films with same properties were deposited on MLCA under optimum RF magneto conditions(Ar 100 %, input power $1\;/cm^2$). After annealing in $450^{\circ}C$ for 1 hr, the anodic bonding of MLCA to Si-wafer was successfully performed at 600 V, $400^{\circ}C$ in - 760 mmHg. Then, the MLCA/Si bonded interface and fabricated Si diaphragm deflection characteristics were analyzed through the actuation test. It is possible to control with accurate deflection of Si diaphragm according to its geometries and its maximum non-linearity is 0.05-008 %FS. Moreover, any damages or separation of MICA/Si bonded interfaces do not occur during actuation test. Therefore, it is expected that anodic bonding technology of MICA/Si wafers could be usefully applied for the fabrication process of high-performance piezoelectric MEMS devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.179-179
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• 2011

관통전극(TSV, Trough Silicon Via) 기술은 전자부품의 소형화, 고성능화, 생산성 향상을 이룰 수 있는 기술이다. Cu는 현재 배선 기술에 적용되고 있고 전기적 저항이 낮아서 TSV filling 재료로 사용된다. 하지만 확산 방지막에 의해 완벽히 감싸지지 않는다면, Cu+은 빠르게 절연막을 통과하여 Si 웨이퍼로 확산된다. 이런 현상은 절연막의 누설과 소자의 오동작 등의 신뢰성 문제를 일으킬 수 있다. 현재 TSV의 제조와 열 및 기계적 응력에 관한 연구는 활발히 진행되고 있으나 Biased-Thermal Stress(BTS) 조건하의 Cu 확산에 관한 연구는 활발하지 않는 것이 실정이다. 이를 위해 본 연구에서는 TSV용 Cu 확산 방지막 Ti에 대해 Cu+의 drift 억제 특성을 조사하였다. 실험을 위해 Cu/확산 방지막/Thermal oxide/n-type Si의 평판 구조를 제작하였고 확산 방지막의 두께에 따른 영향을 조사하기 위해 Ti의 두께를 10 nm에서 100 nm까지 변화하였으며 기존 Cu 배선 공정에서 사용되는 확산 방지막 Ta와 비교하였다. 그리고 Cu+의 drift 측정을 위해 Biased-Thermal Stress 조건(Thermal stress: $275^{\circ}C$, Bias stress: +2MV/cm)에서 Capacitance 및 Timedependent dielectric breakdown(TDDB)를 측정하였다. 그 결과 Time-To Failure(TTF)를 이용하여 Cu+의 drift를 측정할 수 있었으며, 확산 방지막의 두께가 증가할수록 TTF가 증가하였고 물질에 따라 TTF가 변화하였다. 따라서 평판 구조를 이용한 본 실험의 Cu+의 drift 측정 방법은 향후 TSV 구조에서도 적용 가능한 방법으로 생각된다.

• Food Science and Biotechnology
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• v.18 no.6
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• pp.1342-1350
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• 2009

This paper investigates the production and optimization of $\beta$-galactosidase enzyme using synthetic medium by Kluyveromyces lactis NRRL Y-8279 in stirred tank bioreactor. Response surface methodology was used to investigate the effects of fermentation parameters on $\beta$-galactosidase enzyme production. Maximum specific enzyme activity of 4,622.7 U/g was obtained at the optimum levels of process variables (aeration rate 2.21 vvm, agitation speed 173.4 rpm, initial sugar concentration 33.8 g/L, incubation time 24.0 hr). The optimum temperature and pH of the $\beta$-galactosidase enzyme produced under optimized conditions were $37^{\circ}C$ and pH 7.0, respectively. The enzyme was stable over a pH range of 6.0-7.5 and a temperature range of $25-37^{\circ}C$. The $K_m$ and $V_{max}$ values for O-nitrophenol-$\beta$-D-galactopyranoside (ONPG) were 1.20 mM and $1,000\;{\mu}mol/min{\cdot}mg$ protein, respectively. The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in $\beta$-galactosidase enzyme production. Hence, this study fulfills the lack of using mathematical and statistical techniques in optimizing the $\beta$-galactosidase enzyme production in stirred tank bioreactor.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.10
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• pp.465-470
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• 2005

In this paper. an experimental study, for method of increasing the efficiency of electrostatic precipitator for the collection of submicron-sized particles has been studied. All AC electric field was used to induce agglomeration of bipolory charged Particles. .4 bipolar AC-agglomeration system. consisted with a multineedle-mesh discharge system with a control grid, was proposed and investigated. Systematic experiments were carried out to investigate the agglomeration ratio of the AC-agglomeration system as a function of the different grid spacings and grid resistances for the submicron particles generated from liquid prorhane gas burning. The agglomeration ratios, which indicate the particle numbers before and after agglomeration of the test particles in number concentration base, were found to be 0.87, 1.80, 3.86, 9.50 and, 11.00 times for the particle sizes of 0.3. 0.5, 0.7, 1.0, and 2.0$\mu$m at applied voltage of 3.5kV, respectively which showed that the fine particle numbers were decreased while the larger particle numbers were increase greatly.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.3
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• pp.161-166
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• 1999

We investigate the device characteristics of the separated shorted-anode LIGBT (SSA-LIGBT), which suppresses effectively the negative differential resistance regime, by 2-dimensional numerical simulation. The SSA-LIGBT increases the pinch resistance by employing the highly resistive n-drift region as an electron conduction path instead of the lowly resistive n buffer region of the conventional SA-LIGBT. The negative differential resistance regime of the SSA-LIGBT is significantly suppressed as compared with that of the conventional SA-LIGBT. The SSA-LIGBT shows the lower forward voltage drop than that of the conventional SA-LIGBT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.116-119
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• 2002

A different route to the synthesis of $Eu^{3+}$ - activated matrices such as $YAlO_{3}$ and $GdAlO_{3}$ and luminiscent properties of these compounds, were studied. The new route (Combustion method) consist of the redox reactions between the respective metal nitrates and urea in a preheated furnace at ${500^{\circ}C}$. The Phosphor thus obtained were then heated at ${1000^{\circ}C}$ for 2-3 hours to get better luminiscent properties. The incorporation of $Eu^{3+}$ activator in these phosphors were checked by luminiscence investigations. Scanning electron microscopy (SEM) studies were carried out to understand surface morphological features and the particle size. X-ray energy dispersive analysis (EDAX) was also performed for the qualitative analysis of the phosphors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.82-85
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• 2003

This dissertation describes an optimization method for fabricating thick films with superconducting YBCO powders by electrophoresis technique. The lateral alternating applied voltage caused to shake the superconducting powder vertically to the deposition field during the process of the oriented deposition so that it was deposited along the c-axis on the silver tape with shaky-aligned EPD. As the result, the optimized thin film fabrication method was obtained to get more dense and uniform surface morphology as well as the improved critical current density. For commercial utilization and efficiency, in this dissertation, alternating voltage of 25-120 V/cm in frequency of 60Hz was proposed to apply it as a subsidiary source for shaky-flow deposition so that the fabricated thin film showed uniform surface morphology with less voids and cracks and $T_{c.zero}$ of 90 K and the critical current density of $3419A/cm^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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• pp.661-665
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• 2007

This paper presents the electrical properties of SiGe HBTs designed with bottom collector and single metal layer structure for RF power amplifier. Base layer was formed with graded-SiGe/Si structures and the collector place to the bottom of the device. Bottom collector and single metal layer structures could significantly simplify the fabrication process. We studied about the influence of SiGe base thickness, number of emitter fingers and temperature dependence $(<200^{\circ}C)$ on electrical properties. The feasible application in $1{\sim}2GHz$ frequency from measured data $BV_{CEO}{\sim}10V,\;f_T{\sim}14GHz,\;{\beta}{\simeq}110,\;NF{\sim}1dB$ using packaged SiGe HBTs. We will discuss the temperature dependent current flow through the e-b, b-c junctions to understand stability and performance of the device.