• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2771-2776
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• 2000

In this work, the effect of surface treatment of prepreg on the mode I fracture behavior was studied. Unidirectional (0-deg) double cantilever beam (DCB) specimens were used for fracture tests. Two groups of DCB specimens were made: the first group was made of prepregs surface-treated by Ar(sup)+ ion beam under oxygen environment and the second group was made of regular prepregs. For both groups, fracture resistance curve (R-curve) was determined and compared to each other, Results showed that resistance behavior of the first group is better than that of the second group. That is, mode I fracture toughness, G(sub)Ic of the first group is 24% larger than that of the second group. SEM examination shows that the improvement of G(sub)Ic is due to the increase of interfacial strength between plies.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.25-28
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• 2001

In this paper, we have investigated the effects of gas flow rate, rf power, process pressure and Ar addition on reactive ion etching of InP, InGaAs and InAlAs using Sic14 and Cl$_2$ gases. The etch rates were measured by using a surface profiler. The etched profiles, sidewall roughness, and surface morphology were observed by scanning electron microscopy and by atomic force microscopy. The selective etching of InGaAs to InP and InAlAs was studied by varying the etching parameters. It was found that Cl$_2$ gas is more efficient for the selective etching of InGaAs to InAlAs than SiCl$_4$ gas. The etch selectivity of InGaAs to InAlAs is strongly dependent on the rf power and the process pressure.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.229-233
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• 2007

In this study, we carried out an investigation of the etching characteristics(etch rate, selectivity) of $HfO_2$ thin films in the $CH_4/Ar$ inductively coupled plasma. It was found that variations of input power and negative dc-bias voltage are investigated by the monotonic changes of the $HfO_2$ etch rate as it generally expected from the corresponding variations of plasma parameters. At the same time, a change in either gas pressure or in gas mixing ratio result in non-monotonic etch rate that reaches a maximum at 2 Pa and for $CH_4(20%)/Ar(80%)$ gas mixture, respectively. The X-ray photoelectron spectroscopy analysis showed an efficient destruction of the oxide bonds by the ion bombardment as well as showed an accumulation of low volatile reaction products on the etched surface. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the $CH_4-containing$ plasmas.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.25-28
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• 2000

In this study, $Y_2$O$_3$ thin films were etched with inductively coupled plasma (ICP). The etch rate of $Y_2$O$_3$, and the selectivity of $Y_2$O$_3$ to YMnO$_3$ were investigated by varying Cl$_2$/(Cl$_2$+Ar) gas mixing ratio. The maximum etch rate of $Y_2$O$_3$, and the selectivity Of $Y_2$O$_3$ to YMnO$_3$ were 302/min, and 2.4 at Cl$_2$/(Cl$_2$+Ar) gas mixing ratio of 0.2 repectively. In x-ray photoelectron spectroscopy (XPS) analysis, $Y_2$O$_3$ thin film was dominantly etched by Ar ion bombardment, and was assisted by chemical reaction of Cl radical. These results were confirmed by secondary ion mass spectroscopy(SIMS) analysis. YCI, and YCl$_3$ existed at 126.03 a.m.u, and 192.3 a.m.u, respectively

• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.1-4
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• 2013

For the conventionally polished fused silica substrate, an around 100 nm depth redeposition polishing layer was formed on the top of surface. Polishing compounds, densely embedded in the redeposition polishing layer were the dominant factor that limited the laser induced damage threshold (LIDT) of transmission elements in nanosecond laser systems. Chemical etching, super-precise polishing and ion beam etching were employed in different ways to eliminate these absorbers from the substrate. After that, Antireflection (AR) coatings were deposited on these substrates in the same batch and then tested by 1064 nm nano-pulse laser. It was found that among these techniques only the ion beam etching method, which can effectively remove the polishing compound and did not induce extra absorbers during the disposal process, can successfully improve the LIDT of AR coatings.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.218.2-218.2
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• 2014

그래핀은 높은 전기 전도도와 열전도도, 기계적 강도를 가지고 있고 동시에 높은 전자이동도($200,000cm^2{\cdot}V{\cdot}^1{\cdot}s{\cdot}^1$) 특성을 갖는 물질로써 차세대 소재로 각광받고 있다. 하지만 그래핀을 소자에 응용하기 위해서는 전사공정과 lithography 공정 과정에서 발생되는 PMMA(Poly methyl methacrylate) residue를 완벽하게 제거해야 하는 문제점이 있다. 특히, lithography 공정 중 완벽하게 PMMA residue 가 제거되지 않고 잔류해 있을 경우에 소자의 life time, performance에 악영향을 준다는 보고가 있다. 이와같은 문제를 해결하기 위해 화학적 cleaning, 열처리를 통한 cleaning, 전류 인가에 의한 cleaning과 같은 방법들을 이용하여 그래핀의 PMMA residue를 제거하는 공정들이 보고되고 있지만, 화학적 cleaning 방법의 경우 chloroform 이라는 독성물질 사용으로 인해 산업적으로 응용이 어렵고, 열처리 방법은 전극 등의 금속이 $200^{\circ}C$ 이상의 높은 온도에서 장시간 노출될 경우 쉽게 손상을 입으며, 전류 인가에 의한 cleaning 방법은 국부적으로만 효과를 볼 수 있기 때문에 lithography 공정 후 PMMA residue를 효과적으로 제거하기에는 한계를 보이고 있다. 본 연구에서는 Ar을 이용하는 Ion beam 시스템을 통해 beam energy를 제어함으로써 PMMA residue를 효과적으로 제거하는 연구를 진행하였다. 최적화된 플라즈마 발생 조건을 찾기 위해 QMS(Quadrupole Mass Spectrometer)를 이용하여 입사하는 ion energy와 flux 양을 컨트롤 하였고, 250 W에서 최적화된 ion energy distribution 영역이 존재한다는 것을 확인할 수 있었다. 또한, 25 Gauss 정도의 electro-magnetic field를 이용하여 Ar의 ion energy를 10 eV 이하로 낮추어 damage를 최소화함으로써 효과적으로 그래핀을 cleaning 할 수 있었다. Cleaning과정에서 ion bombardment에 의해 발생한 damage는 $250^{\circ}C$에서 6시간 동안 annealing 공정을 거치면서 회복되는 것을 Raman spectroscopy의 D peak ($1335cm{\cdot}^1$) / G peak ($1572cm{\cdot}^1$) ratio 로 확인할 수 있었고, PMMA residue의 cleaning 여부는 G peak ($1580cm{\cdot}^1$)의 blue shift와 2D peak ($2670cm{\cdot}^1$)의 red shift를 통해 확인하였다. 그리고 AFM (Atomic Force Microscopy)을 이용하여 cleaning 공정과정에서 RMS roughness가 4.99 nm에서 2.01 nm로 감소하는 것을 관찰하였다. 마지막으로, PMMA residue의 cleaning 정도를 정량적으로 분석하기 위해 XPS (X-ray Photoelectron Spectroscopy)를 이용하여 sp2 C-C bonding이 74.96%에서 87.66%로 증가함을 확인을 할 수 있었다.

• Journal of the Korean Vacuum Society
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• v.12 no.2
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• pp.136-143
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• 2003

In this paper, high purity RF sputter-type ion source for non-mass separated ion beam deposition was evaluated. The fundamental characteristics of the ion source which is composed of an RF Cu coil and a high purity Cu target (99.9999 %) was studied, and the practical application of Cu thin films for ULSI metallization was discussed. The relationship between the DC target current and the DC target voltage at various RF power and Ar gas pressures was measured, and then preparation conditions for Cu thin films was described. As a result, it was found that the deposition conditions of the target voltage, the target current and the Ar pressure were optimized at -300 V, 240 W and 9 Pa, respectively. The resistivity of Cu films deposited at a bias voltage of -50 V showed a minimum value of 1.8 $\pm$ 0.1 $mu\Omega$cm, which is close to that of Cu bulk (1.67 $mu\Omega$cm).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.162-162
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• 2012

Sub 100 nm의 Complementary Metal-Oxide-Semiconductor (CMOS) 소자를 구동하기 위해서는 2.0 nm 이하의 $SiO_2$ oxide에 해당하는 전기적 특성이 요구된다. 그러나 2.0 nm 이하의 $SiO_2$에서는 누설 전류가 너무 크기 때문에 이를 대체하기 위해서 유전 상수 (dielectric permittivity)가 높은 $HfO_2$ (${\varepsilon}=25$), $Al_2O_3$, $HfO_2/Al_2O_3$ laminate 등의 high-k dielectric 물질들이 연구되고 있다[1]. High-k dielectric 물질의 전기적 특성은 박막 조성, 두께 및 전극과의 계면에 생성되는 계면 층이나 불순물(Impurity) 거동에 크게 의존하므로 High-k dielectric/전극(Metal or Si) 구조에서 조성 및 불순물의 거동에 대한 정확한 평가가 주요 쟁점으로 부각되고 있다. 이를 평가하기 위해 일반적으로 $Ar^+$ ion에 의한 depth profiling 분석이 진행되나 Oxygen 원자의 선택적 식각에 기인된 분석 깊이 분해능(Depth Resolution) 왜곡으로 계면 층의 형성이나 불순물의 거동을 정확하게 평가할 수 없다. 이러한 예로는 $Ta_2O_5$ 및 $SrBi_2Ta_2O_9$와 같은 다 성분 계 산화막에 $Ar^+$ ion 주사 시 발생하는 선택적인 식각(Preferential Sputtering) 때문에 박막의 실제 조성 및 거동을 평가하는 것은 어렵다고 보고된 바 있다[2,3]. 본 연구에서는 $90{\AA}$인 적층 $Hf_xO_y/Al_xO_y/Hf_xO_y$ 구조에서의 불순물 거동 분석 능력 확보 상 주요 인자인 깊이 분해능 개선을 Secondary Ion Mass Spectroscopy(SIMS)의 primary ion 종, impact energy 및 주사 각도를 변화시켜 ~1 nm 수준까지 구현하였다. 이러한 분석 깊이 분해능의 개선은 Low Impact Energy, 입사 이온의 glancing angle 및 Cluster ion 적용에 의존하며 이들 요인의 효과에 대해 비교/고찰하고자 한다.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.813-819
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• 1999

Inner crack-like pores with controlled amount of Ca impurity level in the high purity alumina single crystal sapphire had been created by micro-fabrication technique which includes ion implantation photo-lithography Ar ion milling and hot press technique. The morphological change and the healing of crack-like pore in the Ca doped high purity single crystal alumina during high temperature heat treatment in vacuum were observed using optical microscopy. The hexagonal bridging ligaments were developed and the size of hexagonal bridging ligaments had been increased with temperature and Ca amount and had grown to their corner rounded. It appeared that the hexagonal bridging ligaments would have an equilbrium size with temperature and the amount of Ca addition. Three kinds of crack-like pore healing type were observed. Edge regression and ligament growth were observed from relatively low temperature in the crack-like pore. Edge regression were found in almost all of the crack-like pore but the ligament growth were found only in the several crack-like pores accelerating heating very fast. Flow type healing was observed above $1800^{\circ}C$ and It healed the crack-like pore very slowly.

• Journal of the Korean Vacuum Society
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• v.4 no.1
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• pp.26-31
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• 1995

본 연구에서는 Co/Si 계에 대한 이온선 혼합실험을 온도와 이온선량을 변수로 하여 실시하였고, Co/Si 계에 대한 상형성 과정을 금속/Si 계에 대한 이온선 혼합시의 비정질상 및 결정상 형성예측 모델(ADF Model)과 초기 결정상 예측 모델(PDF Model)을 이용하여 해석하였다. 이온선 혼합은 80KeV 가속기를 이용하여 상온$-400^{\circ}C$의 온도 범위에서 1.0X1015Ar+/$\extrm{cm}^2$-2.0X1016Ar+/$\textrm{cm}^2$의 이온선량을 변화시키면서 실험하였으며 상분석은 투과전자현미경(TEM)과 X선 회절 분석을 이용하였다. Co/Si 계에서 이온선 혼합시 형성되는 초기 결정상은 Co2Si이며 이온선량의 증가에 따라 CoSi로 상전이하였다. 이러한 실험 결과는 비정질상 및 결정상 형성 예측 모델(ADF model)과 초기 결정상 예측모델(PDF model)의 예측결과와 매우 잘 일치하고 있다. 이상의 연구 결과로부터 ADF 모델과 PDF모델을 이용하여 박막에서 형성되는 상을 보다 정확히 예측할 수 있음을 알 수 있었다.