• Journal of the Korean institute of surface engineering
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• v.43 no.3
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• pp.159-164
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• 2010

Surface roughness of deposited or etched film strongly depends on ion bombardment. Relationships between ion bombardment variables and surface roughness are too complicated to model analytically. To overcome this, an empirical neural network model was constructed and applied to a deposition process of silicon nitride (SiN) films. The films were deposited by using a pulsed plasma enhanced chemical vapor deposition system in $SiH_4$-$NH_4$ plasma. Radio frequency source power and duty ratio were varied in the range of 200-800 W and 40-100%. A total of 20 experiments were conducted. A non-invasive ion energy analyzer was used to collect ion energy distribution. The diagnostic variables examined include high (or) low ion energy and high (or low) ion energy flux. Mean surface roughness was measured by using atomic force microscopy. A neural network model relating the diagnostic variables to the surface roughness was constructed and its prediction performance was optimized by using a genetic algorithm. The optimized model yielded an improved performance of about 58% over statistical regression model. The model revealed very interesting features useful for optimization of surface roughness. This includes a reduction in surface roughness either by an increase in ion energy flux at lower ion energy or by an increase in higher ion energy at lower ion energy flux.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.126-126
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• 2009

Noninvasive plasma diagnostic technique is introduced to analyze and characterize HICP (Helmholtz Inductively Coupled Plasma) source during the plasma etching process. The HICP reactor generates plasma mainly through RF source power at 13.56MHz RF power and RF bias power of 12.56MHz is applied to the cathode to independently control ion density and ion energy. For noninvasive sensors, the RF sensor and the OES (Optical emission spectroscopy) were employed since it is possible to obtain both physical and chemical properties of the reactor with plasma etching. The plasma impedance and optical spectra were observed while altering process parameters such as pressure, gas flow, source and bias power during the poly silicon etching process. In this experiment, we have found that data measured from these noninvasive sensors can be correlated to etch results. In this paper, we discuss the relationship between process parameters and the measurement data from RF sensor and OES such as plasma impedance and optical spectra and using these relationships to analyze and characterize H-ICP source.

• Journal of the Korean Vacuum Society
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• v.6 no.4
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• pp.326-336
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• 1997

From the concept that the ion implantation-induced defect is one of the major factors in determining source/drain junction characteristics, high quality ultra-shallow $p^+$-n junctions were formed through the control of ion implantation-induced defects in silicon substrate. In conventional process of the junction formation. $p^+$ source/drain junctions have been formed by $^{49}BF_2^+$ ion implantation followed by the deposition of TEOS(Tetra-Ethyl-Ortho-Silicate) and BPSG(Boro-Phospho-Silicate-Glass) films and subsequent furnace annealing for BPSG reflow. Instead of the conventional process, we proposed a series of new processes for shallow junction formation, which includes the additional low temperature RTA prior to furnace annealing, $^{49}BF_2^+/^{11}B^+$ mixed ion implantation, and the screen oxide removal after ion implantation and subsequent deposition of MTO (Medium Temperature CVD oxide) as an interlayer dielectric. These processes were suggested to enhance the removal of ion implantation-induced defects, resulting in forming high quality shallow junctions.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.143-144
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• 2015

Here we report the Ar-ion milling rates of ultrathin Si and GaAs single crystals. The thickness change is measured using convergent beam electron diffraction (CBED) technique with the help of Bloch wave simulation method. This study suggests the experimental procedures to determine the references for an etching rate to reduce a sample thickness or to remove the damaged sample surface using Ar-ion source.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4644-4651
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• 2022

Due to its short half-life, thoron gas has been assumed to have negligible health hazards on humans compared to radon. But, one of the decay products with a long half-life can make it to be transported to a long distance and to cause a severe internal dose through respiration. Since most commercial radon detectors can not discriminate thoron signals from radon signals, it is very common to overestimate radon doses which in turn result in biased estimation of lung cancer risk in epidemiological studies. Though some methods had been suggested to measure thoron and radon separately, they could not be used for real-time measurement because of CR-39 or LR-115. In this study, an effective method was suggested to measure radon and thoron separately from the free air. It was observed that the activity of thoron decreases exponentially due to delay time caused by a long pipe between two chambers. Therefore from two ion chambers apart in time, it was demonstrated that thoron and radon could be measured separately and simultaneously. We also developed a collimated alpha source and with this source and an SBD, we could convert the ion chamber reading to count rate in cps.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.267-269
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• 2008

본 연구는 이온주입(Ion Implanter)장비의 성능향상과 재현성 있는 Source Head를 개발하기 위한 방법이다. 본 개발은 이온주입설비가 가지고 있는 Cathode 열전자를 이용하여 원자라는 Source Positive의 극성을 생성하여 보다 높은 이온화를 발생하여 많은 시간 동안 사용 가능하도록 하였다. 기존에는 Gas의 손실이 많아 원자의 이온화에 대한 열전자의 소모성을 증가하는 원인을 제공하였으나, 본 개발에서는 원자의 유입방식을 공중 분산방식으로 적용함으로써 열전자의 손실로 발생하는 부분을 억제하는 효과와 Arc Chamber의 압력을 낮게 가지고 갈 수 있고 Chamber의 오염을 억제하는 효과를 얻을 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.311-312
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• 2006

We studied homeotropic alignment effect for a nematic liquid crystal (NLC) on the $SiO_x$, thin film irradiated by the new ion beam method $SiO_x$ thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) and were treated by the DuoPIGatron ion source. A uniform liquid crystal alignment effect was achieved over 2100 eV ion beam energy. Tilt angle were about $90^{\circ}$ and were not affected by various ion beam energy.

• Mass Spectrometry Letters
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• v.4 no.4
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• pp.91-94
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• 2013

We performed computer simulations to improve transmission efficiencies of a dual ion funnel system implemented on an FT-ICR MS. We found that the low m/z range from 50 to 150 could be significantly improved by operating the two ion funnels at different RF amplitudes. These new operational conditions could be applied to analyze metabolome samples, which require high sensitivity in the m/z range from 50 to 1,000.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.5
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• pp.471-477
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• 2007

SCBF(Spherically Convergent Beam Fusion) device has been studied as a neutron source. Neutron production rate is a most important factor for the application of SCBF device and is proportional to the square of the ion current[1]. It is regarded generally that some correlations between the potential well structure and the ion current exist. In this paper, the ion current and potential distribution were calculated in a variety of grid cathode geometries using FEM-FCT method. Single potential well structure was certified inside the grid cathode. The deeper the potential well became, the higher the ion current due to the high electric field near the grid cathode became.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.154.1-154.1
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• 2014

Indium gallium zinc oxide (IGZO)는 차세대 디스플레이 평판 패널에 사용되는 반도체 화합물의 일종으로 최근 주목받고 있는 물질의 하나이다. 기존의 IGZO를 사용하여 박막을 증착한 뒤 표면 처리를 통해 박막의 특성 변화에 대한 연구들이 진행되어 왔으며, 기존의 연구들은 plasma 환경에 노출을 시켜 간접적인 plasma treatment를 통해 박막의 특성을 향상시켜 왔다. 본 연구에서는 기존의 plasma treatment에서 발견된 방식인 ion beam treatment를 통해 플라즈마를 직접적으로 표면에 조사하여 박막의 특성 변화를 알아보았다. 한국표준과학연구원에서 자체 제작한 chamber를 이용하여 RF sputter로 Si wafer 위에 IGZO 박막을 증착하고 수소 ion beam treatment를 한 뒤, SEM과 XPS를 사용하여 박막 표면의 물성 변화를 분석하였다. 실험에 사용된 chamber에는 sputter gun과 ion beam이 함께 장착되어 있으며, scroll pump와 TMP를 사용하여 pressure를 유지하였다. 실험 시 base pressure는 $1.4{\times}10^{-6}Torr$였다. RF power 150 W. ion beam power 2,000 V에서 실험을 진행하였다.