• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1432-1433
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• 2007

반도체 제조공정에서 널리 쓰이고 있는 플라즈마 에칭프로세스는 기판의 물질을 선택적으로 제거할 때 사용하는 방법이다. 컴퓨터 시뮬레이션을 이용하여 플라즈마 에칭공정을 예측하기 위한 많은 노력이 행하여져 왔다. 그러나 많은 연구에서 플라즈마와 쉬스영역을 따로 모델링하거나 PIC-MC 방법을 이용하였다. 본 논문에서는 반도체 에칭 공정에 사용되는 플라즈마와 플라즈마 쉬스를 상용 코드인 Multiphysics를 사용하여 동시에 시뮬레이션하고 실험결과와의 일치성을 보이고자 한다.

• 한국표면공학회지
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• 제42권3호
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• pp.133-138
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• 2009

Effects of bipolar pulse driving frequency between 50 kHz and 250 kHz on the discharge shapes were analyzed by measuring plasma characteristics by OES (Optical Emission Spectroscopy) and Langmuir probe. Plasma characteristics were modeled by a simple electric field analysis and fluid plasma modeling. Discharge shapes by a continuous dc and bipolar pulsed dc were different as a dome-type and a vertical column-type at the cathode. From OES, the intensity of 811.5 nm wavelength, the one of the main peaks of Ar, decreased to about 43% from a continuous dc to 100 kHz. For increasing from 100 kHz to 250 kHz, the intensity of 811.5 nm wavelength also decreased by 46%. The electron density decreased by 74% and the electron temperature increased by 36% at the specific position due to the smaller and denser discharge shape for increasing pulse frequency. Through the numerical analysis, the negative glow shape of a continuous dc were similar to the electric potential distribution by FEM (Finite Element Method). For the bipolar pulsed dc, we found that the electron temperature increased to maximum 10 eV due to the voltage spikes by the fast electron acceleration generated in pre-sheath. This may induce the electrons and ions from plasma to increase the energetic substrate bombardment for the dense thin film growth.

• 한국진공학회지
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• 제3권2호
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• pp.179-185
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• 1994

음극에 DLC 필름이 놓여져 있는 용량결합형의 RF 플라즈마 장치에서 Ar가스에 의한 방전에서 발생된 입자의 분포를 레이져 산란에 의하여 관측하였다. 발생된 입자들은 플라즈마와 sheath의 경계면 에서 높은 밀도의 구름을 이루었으며 시간에 따라 주기적인 분포의 변화가 반복되었다, 입자 구름의 발 생은 플라즈마 물성의 변화를 야기하였으며 그 결과로 심한 self-bias 전위의 감소현상이 관측되었다. 입자 구름분포의 시간에 따른 변화와 같은 주기의 self-bias 플라즈마전위의 진동현상이 가열된 fast-scanning langmuir 탐침에 의하여 관측되었다. 이결과는 입자 표면에로의 음전하 누적에 따른 전체 음전하의 이동도 감소에 의한 것으로 해석된다. 또한 방출 분광법에 의하여 입자오염상태의 Ar 플라즈 마와 정상상태의 Ar 플라즈마의 방출 선세기의 변화를 관측하였는데 입자구름 오염시의 2차전자 차폐 현상에 의해 높은 문턱 에너지를 가진 Ar II 선의 세기 감소현상이 나타났다.

• Radiation Oncology Journal
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• 제32권3호
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• pp.208-212
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• 2014

Marfan syndrome is one of the collagen vascular diseases that theoretically predisposes patients to excessive radiation-induced fibrosis yet there is minimal published literature regarding this clinical scenario. We present a patient with a history of Marfan syndrome requiring radiation for a diagnosis of a right brachial plexus malignant nerve sheath tumor. It has been suggested that plasma transforming growth factor beta 1 (TGF-${\beta}1$) can be monitored as a predictor of subsequent fibrosis in this population of high risk patients. We therefore monitored the patient's TGF-${\beta}1$ level during and after treatment. Despite maintaining stable levels of plasma TGF-${\beta}1$, our patient still developed extensive fibrosis resulting in impaired range of motion. Our case reports presents a review of the literature of patients with Marfan syndrome requiring radiation therapy and the limitations of serum markers on predicting long-term toxicity.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.245-250
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• 2004

The discharge current oscillation has been measured for various hollow anode widths and its axial positions using a 1㎾-class anode layer hall thruster. As a result, there were thresholds of magnetic flux density for stable discharge. The plasma structure inside the hollow anode was numerically analyzed using the fully kinetic 2D3V Particle-in-Cell (PIC) and Direct Simulation Monte Carlo (DSMC) methods. The results reproduced both stable and unstable operation modes. In the stable operation case, which corresponds to the case with low magnetic flux, the plasma penetrated into the hollow anode deeper than the case with higher magnetic flux density case. This suggests that comparably large substantial anode area should contribute to stable operation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1657-1658
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• 2006

An external electrode fluorescent lamps (EEFLs) have the advantage of a long lifetime in the early stages of the study on plasma discharge, interest in the lamp continues. Studies on the operation of external electrode fluorescent lamps have focused mainly on its use of a type of high frequency (MHz). By performing high brightness using a square wave operation method with the low frequency below 100kHz, which is applied to a narrowed tube type lamp that has several mm of lamp diameter. To solve these problems of CCFL, EEFL (External Electrode Fluorescent Lamp) is introduced. Because electrode of EEFL is on the outer surface of discharge tube, the electrode is perfectly prevented from the sputtering by accelerated ions. And it is possible to drive the many CCFLs at the same time, because EEFL shows the positively resistant characteristic. But EEFL has the large non-radiative power loss in sheath. In this study the novel electrode structure was introduced in order to reduce non-radiative power loss in sheath of EEFL. The novel electrode structure comes from the idea to combine conceptually capacitive discharge with inductive discharge. Thus, this study verifies the change in the optical characteristics according to the change in electrode structure through a Maxwell's electromagnetic field simulation and examines the relationship between the change in the EEFL electrode structure and brightness by measuring the optical characteristics.

• 한국표면공학회지
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• 제37권1호
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• pp.5-12
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• 2004

The enhancement of adhesion for Cu film on polycarbonate (PC) surface with the $Ar/O_2$ gas plasma treatment and dc-bias sputtering was studied. The plasma treatment with this reactive mixture changes the chemical property of PC surface into hydrophllic one, which is shown by the variation of contact angle with surface modification. The micro surface roughness that also gives the high adhesive environment is increased by the $Ar/O_2$ gas plasma treatment. These results were observed distinctly from the atomic force microscopy (AFM). The negative substrate dc-bias effect for the Cu adhesion on PC was also investifated. Accelerated $Ar^{+}$ lons in sheath area of anode bombard the bare surface of PC during initial stage of dc bias sputtering. PC substrate. therefore, has severe roughen and hydrophilic surface due to the physical etching process with more activated functional group. As dc-bias sputtering process proceeds, morphology of Cu film shows better step coverage and dense layer. The results of peel test show the evidence of superiority of bias sputtering for the adhesion between metal Cu and PC.C.

• 한국표면공학회지
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• 제41권3호
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• pp.94-101
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• 2008

A new convenient magnet array module is designed to investigate effects of magnetic field array on magnetron discharge characteristics. Magnetic field analysis showed good agreement of measured discharge region by a CCD device which has a high quantum efficiency over visible wavelength range. OES (optical emission spectroscopy) showed major emission peaks are from electronic transitions in 400 nm range and 800 nm range. Effects of driving voltage characteristics were analyzed in a point of electron drift trajectories and ionizing collision frequencies. Pulsed dc with a fast rising and falling time was analyzed to have potential to increase ionization collisions by putting a burst of hot electrons and to raise sheath potential. From measured voltage and current waveform, maximum of -1000 V peak was generated with $-400\;V_{rms}$ conditions. Possibility of a properly designed magnetron cathode was shown to be used as a melting device. Cu was successfully melted with power density of a several tens of $W/cm^2$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.96-96
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• 2016

Nanotechnology mostly employs nano-materials and nano-structures with distinctive properties based on their size, structure, and composition. It is quite difficult to produce nano-materials and nano-structures with identical sizes, structures, and compositions in large quantities, because of spatiotemporal fluctuation of production processes. In other words, fluctuation is the bottleneck in nanotechnology. We propose three strategies to suppress such fluctuations: employing 1) difference between linear and nonlinear phenomena, 2) difference in time constants, and 3) nucleation as a bottleneck phenomenon. We are also developing nano- and micro-scale guided assembly using plasmas as a plasma nanofabrication.1-5) We manipulate nano- and micro-objects using electrostatic, electromagnetic, ion drag, neutral drag, and optical forces. The accuracy of positioning the objects depends on fluctuation of position and energy of an object in plasmas. Here we evaluate such fluctuations and discuss the mechanism behind them. We conducted in-situ evaluation of local plasma potential fluctuation using tracking analysis of fine particles (=objects) in plasmas. Experiments were carried out with a radio frequency low-pressure plasma reactor, where we set two quartz windows at the top and bottom of the reactor. Ar plasmas were generated at 200 Pa by applying 13.56MHz, 450V peak-to-peak voltage. The injected fine particles were monodisperse methyl methacrylate-polymer spheres of $10{\mu}m$ in diameter. Fine particles were injected into the reactor and were suspended around the plasma/sheath boundary near the powered electrode. We observed binary collision of fine particles with a high-speed camera. The frame rate was 1000-10000 fps. Time evolution of their distance from the center of mass was measured by tracking analysis of the two particles. Kinetic energy during the collision was obtained from the result. Potential energy formed between the two particles was deduced by assuming the potential energy plus the kinetic energy is constant. The interaction potential is fluctuated during the collision. Maximum amplitude of the fluctuation is 25eV, and the average is 8eV. The fluctuation can be caused by neutral molecule collisions, ion collisions, and fluctuation of electrostatic force. Among theses possible causes, fluctuation of electrostatic force may be main one, because the fine particle has a large negative charge of -17000e and the corresponding electrostatic force is large compared to other forces.

• 한국동물학회지
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• 제28권1호
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• pp.44-59
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• 1985

가옥내에 서식하는 바퀴 (Blattella germanica Linne)의 後腸을 回腸과 直腸部로 구분하여, 그들을 구성하는 上皮細胞의 微細構造를 관찰하였다. 回腸은 扁平 혹은 立方型의 細胞들이 單層上皮를 만들며 그 內面은 cuticular intima로 덮여 있었다. 細胞들은 細胞器官이 고르게 발달하여 吸收細胞의 形態를 하였으며, 細胞質內에서 동심원적인 環狀構造를 하는 層板狀 結晶體, "spherites"가 많이 관찰됨이 특징이었다. 直腸은 圓柱狀인 圓柱狀吸收細胞의 尖端部原形質膜은 微細絨毛로 변형되었고, 側部原形質膜은 약 200$\\AA$간격으로 심하게 주름이 잡혔으며 그 사이에는 크게 발달한 mitochondria가 밀착하여 mitochondrial-scalarifrom complexes를 형성하였다. 그리고 인접 細胞間에는 많은 細胞間隙을 만들며, 그 사이 사이에는 septate junction과 desmosomes 등으로 연접된 것이 여러 곳에서 관찰되었다. 基底細胞는 납작한 杯모양으로서 細胞質의 電子密度가 높아 검게 보였으며, 그 내에는 Golgi complex, endoplasmic reticulum 그리고 mitochondria 등 細胞器官들이 발달되었고 膜의 구조 등으로 미루어 보아 역시 吸收機能을 가진 細胞임을 확인하였다. 한편 直腸의 上皮層과 hemolymph 사이에서 壁의 역할을 하는 basal sheath가 基底面을 따라 평행하게 부착되어 있고, 그 basal sheath와 근육층 사이에는 結合組織이 넓은 subepithelial space를 만들어서 그 내에는 많은 氣官小支들과 밀도가 높은 顆粒들을 갖는 軸索이 분포하고 있었다.