• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.799-803
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• 2018

We demonstrated memory thin-film transistors (MTFTs) with organic ferroelectric polymer poly(vinylidene fluoride-co-trifluoroethylene) and an amorphous oxide semiconducting indium gallium zinc oxide channel on the elastomeric substrate. The dielectric constant for the P(VDF-TrFE) thin film prepared on the elastomeric substrate was calculated to be 10 at a high frequency of 1 MHz. The voltage-dependent capacitance variations showed typical butterfly-shaped hysteresis behaviors owing to the polarization reversal in the film. The carrier mobility and memory on/off ratio of the MTFTs showed $15cm^2V^{-1}s^{-1}$ and $10^6$, respectively. This result indicates that the P(VDF-TrFE) film prepared on the elastomeric substrate exhibits ferroelectric natures. The fabricated MTFTs exhibited sufficiently encouraging device characteristics even on the elastomeric substrate to realize mechanically stretchable nonvolatile memory devices.

• Safety and Health at Work
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• v.12 no.3
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• pp.403-415
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• 2021

Background: This study aimed to assess the possibility of benzene exposure in workers of a Korean semiconductor manufacturing company by reviewing the issued patents. Methods: A systematic patent search was conducted with the Google "Advanced Patent Search" engine using the keywords "semiconductor" and "benzene" combined with all of the words accessed on January 24, 2016. Results: As a result of the search, we reviewed 75 patent documents filed by a Korean semiconductor manufacturing company from 1994 to 2010. From 22 patents, we found that benzene could have been used as one of the carbon sources in chemical vapor deposition for capacitor; as diamond-like carbon for solar cell, graphene formation, or etching for transition metal thin film; and as a solvent for dielectric film, silicon oxide layer, nanomaterials, photoresist, rise for immersion lithography, electrophotography, and quantum dot ink. Conclusion: Considering the date of patent filing, it is possible that workers in the chemical vapor deposition, immersion lithography, and graphene formation processes could be exposed to benzene from 1996 to 2010.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.5
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• pp.8-14
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• 2007

In this paper, $HfO_2$/Hf stacked film has been applied as the gate dielectric in MOS devices. The $HfO_2$ thin film was deposited on p-type (100) silicon wafers by atomic layer deposition (ALD) using TEMAHf and $O_3$ as precursors. Prior to the deposition of the $HfO_2$ film, a thin Hf metal layer was deposited as an intermediate layer. Round-type MOS capacitors have been fabricated on Si substrates with 2000${\AA}$-thick Al or Pt top electrode. The prepared film showed the stoichiometric components. At the $HfO_2$/Si interface, both Hf-Si and Hf-Si-O bonds were observed, instead of Si-O bond. The sandwiched Hf metal layer suppressed the growing of $SiO_x$ layer so that $HfSi_xO_y$ layer was achieved. It seems that the intermediate Hf metal layer has a benefit for the enhancement of electric characteristics of gate dielectric in $HfO_2$/Si structure.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.4
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• pp.136-142
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• 2022

The crystal structure, grain growth behavior, and dielectric properties of BaTiO₃ have been studied with the addition of Dy₂O₃. The powders were synthesized at ratios of (100-x)BaTiO₃-xDy₂O₃ (mol%, x = 0, 0.5, 1.0, 2.0) by a conventional solid-state synthesis, and the powder compacts were sintered at 1250℃ for 2 hours in air. As the amount of added Dy₂O₃ was increased, the crystal structure of the sintered samples changed from a tetragonal to a pseudo-cubic structure, and the tetragonality decreased. In addition, a secondary phase of Ba₁₂Dy_4.67Ti₈O₃₅ appeared when Dy₂O₃ was added. The average grain size after sintering decreased and abnormal grains appeared as the amount of Dy₂O₃ increased. It can be explained that the grain growth behavior of the Dy₂O₃ added-BaTiO₃ occurs due to the two-dimensional nucleation and growth, and is governed by the interface reaction. Further, the correlation between crystal structure, microstructure, and dielectric properties was discussed.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.169-174
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• 2008

The structural and electrical properties of amorphous $BaSm_2Ti_4O_{12}$ (BSmT) films on a $TiN/SiO_2/Si$ substrate deposited using a RF magnetron sputtering method were investigated. The deposition of BSmT films was carried out at $300^{\circ}C$ in a mixed oxygen and argon ($O_2$ : Ar = 1 : 4) atmosphere with a total pressure of 8.0 mTorr. In particular, a 45 nm-thick amorphous BSmT film exhibited a high capacitance density and low dissipation factor of $7.60\;fF/{\mu}m2$ and 1.3%, respectively, with a dielectric constant of 38 at 100 kHz. Its capacitance showed very little change, even in GHz ranges from 1.0 GHz to 6.0 GHz. The quality factor of the BSmT film was as high as 67 at 6 GHz. The leakage current density of the BSmT film was also very low, at approximately $5.11\;nA/cm^2$ at 2 V; its conduction mechanism was explained by the the Poole-Frenkel emission. The quadratic voltage coefficient of capacitance of the BSmT film was approximately $698\;ppm/V^2$, which is higher than the required value (<$100\;ppm/V^2$) for RF application. This could be reduced by improving the process condition. The temperature coefficient of capacitance of the film was low at nearly $296\;ppm/^{\circ}C$ at 100 kHz. Therefore, amorphous BSmT grown on a TiN substrate is a viable candidate material for a metal-insulator-metal capacitor.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.77-83
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• 2011

In this thesis, 50W Doherty amplifier was designed and implemented for Beyond 3G's repeater and base-station. Auxiliary amplifier of doherty amplifier was implemented by Gate bias control circuit. Though gate bias control circuit solved auxiliary's bias problem, output characteristics of doherty amplifier was limited. To enhance the output characteristic relativize Drain control circuit And To improve power efficiency make 3-way Doherty power amplifier. therefore, 3-way GDCD (Gate and Drain bias Control Doherty) power amplifier is embodied to drain bias circuit for General Doherty power amplifier. The 3-way GDCD power amplifier composed of matching circuit with chip capacitor and micro strip line using FR4 dielectric substance of specific inductive capacity(${\varepsilon}r$) 4.6, dielectric substance height(H) 30 Mills, and 2.68 Mills(2 oz) of copper plate thickness(T). Experiment result satisfied specification of amplifier with gains are 57.03 dB in 2.11 ~ 2.17 GHz, 3GPP frequency band, PEP output is 50.30 dBm, W-CDMA average power is 47.01 dBm, and ACLR characteristics at 5MHz offset frequency band station is -40.45 dBc. Especially, 3-way DCHD power amplifier showed excellence efficiency performance improvement in same ACLR than general doherty power amplifier.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.407-410
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• 1998

The characteristics of $(Ba,Sr)TiO_3$[BST] thin films with the variation of $O_2/Ar$ ratio in sputtering gas deposited on $RuO_2$ bottom electrode were investigated. Dielectric constant of BST film increases from 135 to 190 with increasing oxygen partial pressure from 10 to 50, which is mainly due to the improved crystallinity of BST film. The instability of $RuO_2$ surface in $BST/RuO_2$ interface and the increase in the surface roughness of BST thin films with higher $O_2/Ar$ ratio appeared to play an important roles on the degradation of the leakage current characteristics of $Al/BST/RuO_2$ capacitor with various $O_2/Ar$ ratio in sputtering gas. As a consequence, the leakage current of BST thin film showed the lowest value of $1.9{\times}10^{-7}\; A/{\textrm}{cm}^2$ at $O_2/Ar{\approx}1/9$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.172-172
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• 2009

$BaTiO_3$는 perovskite 구조를 가지는 대표적인 강유전체 재료로서 MLCC(Multi Layer Ceramic Capacitor), PTC thermistor등에 널리 사용되어지고 있다. 최근 고용량 MLCC 의 상업화와 함께 나노크기를 갖는 tetragonal phase의 $BaTiO_3$ 입자를 합성하기 위한 다양한 제조방법이 제시되고 있다. 또한 유전 특성과 온도특성 및 신뢰성을 향상시키기 위해 많은 첨가제들이 연구되어지고 있다. 따라서 이 번 연구에서는 선행 연구를 통해 얻어진 high energy mill을 이용한 고상반응법으로 제조된 $BaTiO_3$를 사용하였으며, 제조된 $BaTiO_3$ 분말에 glass frit를 첨가하여 소결온도 및 유전특성의 변화를 관찰하였다. 제조된 $BaTiO_3$ 분말은 200nm이하의 구형화와 균일한 입자크기를 보였으며, 선행연구를 통해 최적화된 glass frit의 양인 2.53wt%를 첨가하였고 1170, 1200, $1230^{\circ}C$에서 소결하여 소결온도에 따른 변화를 관찰하였다. 실험방법으로는 원료를 혼합하기 위하여 24시간 ball-mill을 이용하여 혼합하였으며, $\Phi15$로 성형하여 소결을 진행하였다. 실험진행 결과 모든 시편에서의 비유전율은 glass frit가 첨가되지 않은 조성보다 높게 나타났으며, $1200^{\circ}C$에서 소결한 시편의 비유전율($\varepsilon_r$)은 2300으로 glass frit가 첨가되지 않은 조성과 비교하여 21% 증가하여 최대치를 나타냈다. 또한 소결온도 $1200^{\circ}C$ 이상에서의 모든 시편에서는 95% 이상의 상대밀도를 나타내어, glass frit가 소결조제로써의 역할을 하는 것으로 나타났다. 따라서 본 연구를 통해 glass frit첨가로 인한 소결온도 감소 및 유전특성이 증가하는 것을 확인 하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.760-767
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• 2005

In this paper, we proposed a new type SIR bandpass filter using DAMLs. This filter is consisted of 2 layers with MEMS resonator layer and CPW feed line. DAMLs ring resonator is elevated with $10{\mu}m$ height from GaAs substrate. Using MEMS processing, we are able to realize SIR bandpass filter easily. Furthermore it is useful to integrate on conventional MMICs because it has CPW interfaces and ring resonator is isolated from substrate by air-gap. We optimized and measured the results that $S_{21}$ attenuation at rejected band is over 15 dB, insertion loss is inside the limit of 3 dB, and relative bandwidth is about $10\%$ at 60 GHz.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.5
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• pp.791-796
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• 2017

In this study, we investigated the influence of the fabrication process of stacked capacitors on the cell capacitance by using Load Lock (L/L) LPCVD system for dielectric thin film of DRAM capacitor. As a result, it was confirmed that the capacitance difference of about 3-4 fF is obtained by reducing the effective thickness of the oxide film by about $6{\AA}$ compared to the conventional non-L/L device. In addition, Cs was found to be about 3-6 fF lower than the calculated value, even though the measurement range of the thickness of the nitride film as an insulating film was in a normal management range. This is because the node poly FI CD is managed at the upper limit of the spec, resulting in a decrease in cell surface area, which indicates a Cs reduction of about 2fF. Therefore, it is necessary to control the thickness of insulating film and CD management within 10% of the spec center value in order to secure stable Cs.