• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.406-406
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• 2010

일반적으로, 나노스케일의 MOS 소자에서는 게이트 절연체 두께가 감소함에 따라 tunneling effect의 증가로 인해 PID (plasma induced damage)로 인한 소자 특성 저하 현상을 감소하는 추세로 알려져 있다. 하지만 요즘 많이 사용되고 있는 high-k 게이트 절연체의 경우에는 오히려 더 많은 charge들이 trapping 되면서 PID가 오히려 더 심각해지는 현상이 나타나고 있다. 이러한 high-k 게이트 식각 시 현재는 주로 Hf-based wet etch나 dry etch가 사용되고 있지만 gate edge 영역에서 high-k 게이트 절연체의 undercut 현상이나 PID에 의한 소자특성 저하가 보고되고 있다. 본 연구에서는 이에 차세대 MOS 소자의 gate stack 구조중 issue화 되고 있는 metal gate 층과 gate dielectric 층의 식각공정에 각각 중성빔 식각과 중성빔 원자층 식각을 적용하여 전기적 손상 없이 원자레벨의 정확한 식각 조절을 해줄 수 있는 새로운 two step 식각 공정에 대한 연구를 진행하였다. 먼저 TiN metal gate 층의 식각을 위해 HBr과 $Cl_2$ 혼합가스를 사용한 중성빔 식각기술을 적용하여 100 eV 이하의 에너지 조건에서 하부층인 $HfO_2$와 거의 무한대의 식각 선택비를 얻었다. 하지만 100 eV 조건에서는 낮은 에너지에 의한 빔 스케터링으로 실제 패턴 식각시 etch foot이 발생되는 현상이 관찰되었으며, 이를 해결하기 위하여 먼저 높은 에너지로 식각을 진행하고 $HfO_2$와의 계면 근처에서 100 eV로 식각을 해주는 two step 방법을 사용하였다. 그 결과 anistropic 하고 하부층에 etch stop된 식각 형상을 관찰할 수 있었다. 다음으로 3.5nm의 매우 얇은 $HfO_2$ gate dielectric 층의 정확한 식각 깊이 조절을 위해 $BCl_3$와 Ar 가스를 이용한 중성빔 원자층 식각기술을 적용하여 $1.2\;{\AA}$/cycle의 단일막 식각 조건을 확립하고 약 30 cycle 공정시 3.5nm 두께의 $HfO_2$ 층이 완벽히 제거됨을 관찰할 수 있었다. 뿐만 아니라, vertical 한 식각 형상 및 향상된 표면 roughness를 transmission electron microscope(TEM)과 atomic force microscope (AFM)으로 관찰할 수 있었다. 이러한 중성빔 식각과 중성빔 원자층 식각기술이 결합된 새로운 gate recess 공정을 실제 MOSFET 소자에 적용하여 기존 식각 방법으로 제작된 소자 결과를 비교해 본 결과 gate leakage current가 약 one order 정도 개선되었음을 확인할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2003.08a
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• pp.164-164
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• 2003

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.5
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• pp.87-92
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• 1985

A simple method to derive EID function which is necessary to compensate for the pro-ximity effect in electron-beam lithography is presented. Using optimization techniques, parameters of EID function is derived and well agreed with experimental valuta.

• Korean journal of applied entomology
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• v.60 no.2
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• pp.255-262
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• 2021

The potato tuber moth, Phthorimaea operculella (Zeller) has been known as a quarantine pest of potato. This study investigated inhibition doses of electron beam irradiation (EBM) by comparing their effects on the development and reproduction and DNA damage of the insect pest. Eggs (0-12 h old), larvae (3^rd and 5^th instar), pupae (less than 1 d old after pupation) and adults (less than 1 d old after emergence) were irradiated with increasing doses of EBM. The EBM with 150 Gy could not completely prevent the hatchability of eggs and pupation of the hatched larvae. The hatchability from the irradiated eggs were 19.3%. However, adult emergence from the irradiated eggs were completely inhibited. When 3^rd and 5^th instar larvae were irradiated at 100 Gy, the adult emergence from the irradiated larvae and the fecundity of the adults were completely inhibited. When pupae and adults were irradiated at 300 Gy and 400 Gy, respectively, the hatchability of the F₁ eggs was completely inhibited. The alkaline comet assay on the level of DNA damage by EBM in P. operculella adults indicates that the EBM increased DNA damage level in a dose-dependent manner, and the damage was repaired in a time-dependent manner. These results may recommend EBM of 150 Gy as a phytosanitary treatment for P. operculella. However further confirmative study is required for the practical application of this EBM dose for P. operculella disinfestation.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.4
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• pp.276-284
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• 2000

The acoustic emission (AE) behavior of reinforced concrete beams tested under flexural loading was investigated to characterize and identify the source of damage. This research was aimed at identifying the characteristic AE response associated with micro-crack development, localized crack propagation, corrosion, and debonding of the reinforcing steel. Concrete beams were prepared to isolate the damage mechanisms by using plain, notched-plain, reinforced, and corroded-reinforced specimens. The beams were tested using four-point cyclic step-loading. The AE response was analyzed to obtain key parameters such as the time history of AE events, the total number and rate of AE events, and the characteristic features of the waveform. Initial analysis of the AE signal has shown that a clear difference in the AE response is observed depending on the source of the damage. The Felicity ratio exhibited a correlation with the overall damage level, while the number of AE events during unloading can be an effective criterion to estimate the level of corrosion distress in reinforced concrete structures. Consequently, AE measurement characterization appears to provide a promising approach for estimating the level of deterioration in reinforced concrete structure.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.272-277
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• 1994

The damage of a thin film of Rd6G dye was probed by Surface Second-Harmonic Generation(SSHG) method. A portion of the Rd6G thin film on glass substrate was damaged by 532 nm laser beam, and the damage was probed by detecting intensity variation of SSHG. The result was confirmed through direct observation with optical microscope.oscope.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.297-297
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• 2013

최근 각종 폴리머 및 강판과 같은 유연소재의 수요 증가로 인해 유연소재 표면의 전처리, 증착 및 기능성 부여를 위한 이온빔 또는 플라즈마 표면처리 기술이 세계적으로 활발히 연구개발 되고 있으며, 유연소재 표면처리 공정의 고속화 및 대면적화 기술이 요구되고 있다. 유연소재의 고속 및 대면적 표면처리 기술개발을 위해서는 Roll-to-Roll 공정에 적용 가능한 광폭 선형이온소스 기술 개발이 필요하다. 본 연구에서는 1.55 m급 광폭 Anode Layer 선형이온소스를 개발하였으며, 이온빔 인출 균일도 및 에너지 분포 특성을 평가하였다. 특히, 본 선형이온 소스 개발 시 시뮬레이션 연구를 통해 이온소소의 이온 인출 특성 및 내구성 향상을 위한 최적 구조를 설계하였다. 본 연구에서 개발한 선형이온소스는 최대 5 kV의 방전 전압 조건에서 평균 1.5 keV의 이온에너지를 가지는 Ar 이온빔이 1.55 m 폭에서 약 4.2%의 균일도를 보였다. 표면 처리 성능 평가시(Si wafer 기준) 소스와 기판과 거리 100 mm에서 에칭율은 15 nm/s였고, 이는 다른 표면처리 이온소스 대비 높은 효율을 나타냄을 확인할 수 있었다. 또한 4시간 이상 운전시에도 안정적인 인출 빔 전류 밀도를 확인하였으며, 소스 내부의 효율적인 냉각 구조로 인한 열손상은 발견되지 않았다.

• Composites Research
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• v.30 no.5
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• pp.297-302
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• 2017

Finite element analysis of T-beam laminate structure under bending-torsional loading was conducted to prevent the delamination which is the major failure behavior on laminated composites. Three-dimensional preform, which is that fabric is braided through thickness direction, is suggested from the laminate analysis. The analysis aimed to optimize the fiber ratio in laminated composites. After it is suggested that guideline for design of T-beam structure using commercial software ANSYS Composites PrePost. The results show that strength of T-beam structure is increased 21.6% when the fiber density along with beam length direction is two times bigger than transverse direction. It is expected that development of high strength T-beam structure using designed three-dimensional preform.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.219-226
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• 2005

In this study, the problem formulation and solution technique using genetic algorithms for design optimization of laminate composite cylindrical beam section are presented. The hollow cylindrical beams we usually used in the wheel chair. If the weight of wheel chair is reduced, it will lead to huge improvement in passenger's mobility and comfort. In this context, the replacement of steel by high performance and light weight composite material along with optimal design will be a good contribution in the process of weight reduction of a wheel chair. An artificial genetics approach for the design optimization of hollow cylindrical composite beam is presented. On applying the genetic algorithm, the optimal dimensions of hollow cylindrical composite beams which have equivalent rigidities to those of corresponding hollow cylindrical steel beams are obtained. Also structural analysis is conducted on the entire wheel chair structure incorporating Tsai-Wu failure criteria. The maximum Tsai-Wu failure criteria index is $0.192\times10^{-3}$ which is moth less than value of 1.00 indicating no failure is observed under excessive loading condition. It is found that the substitution of steel by composite material could reduce the weight of wheel chair up to 45%.

• Journal of the Korean Vacuum Society
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• v.8 no.1
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• pp.36-42
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• 1999

Field emission behaviors from diamond-like carbon films were investigated. The films were deposited on n-type Si wafer by ion beam sputtering method using 3 cm Kaufman type ion source. Regardless of the film thicknesses and atomic bond structure, the emission current was much enhanced by electrical breakdown between anode and the film surface. The effective work function was estimated to be about 0.1 eV. In order to identify the emission site, tungsten tip was scanned the damaged region damaged region but localized to a specific site. Analysis using Auger electron spectroscopy and SEM shows that SiC compound was not a sufficient condition for the electron emission. This result showed that the enhanced emission was mainly due to the changes in the chemical bond of the damaged region rather than the enhanced electric field caused by the morphological change.