• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.369.2-369.2
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• 2014

Diamond-like Carbon(DLC) films doping Si were deposited by linear ion source(LIS)-physical vapor deposition method on Si wafer. We have studied the effects of Si content on friction and wear properties of DLC films and the characteristics of the films were investigated using Nano-indentation, Micro raman spectroscopy, Field Emission-Scanning Electron Microscope (FM-SEM) and X-ray Photoelectron Spectroscopy (XPS). The films has been various low-friction and low-stress by varying the flow rates of silane gas. Under the about 2% of Si doping is very suitable for improving the adhesion of films and reducing internal stress while maintaining the surfaces hardness of DLC films. Linear ion source (LIS)를 사용하여 Si wafer위에 Si 이온이 첨가된 DLC 박막을 증착하였다. 참가된Si 이온의 양에 따라 DLC 박막에 미치는 영향을 분석하기 위하여 마찰 계수 및 경도를 비교하였고, Micro raman spectroscopy, Field Emission-Scanning Electron Microscope (FM-SEM) and X-ray Photoelectron Spectroscopy (XPS)를 통하여 표면 상태를 분석하였다. 천체 주입된 가스량의 약 2%까지 Si 이온 주입이 늘어날수록 DLC 박막의 마찰계수는 낮아졌고, 경도는 Si 이온이 주입되지 않았을 경우와 비슷한 값(약 20~23 GPa)을 가졌다. 2% 이상의 주입량에서는 마찰계수는 주입량이 늘어날수록 높아졌으며 경도는 떨어지는 경향을 보였다. 이는 Si이온이 2%이하로 첨가되었을 경우, DLC 박막의 생성시 탄소 이온들의 결합 Stress를 줄여 마찰계수가 줄어든다고 볼 수 있으며, 그 양이 2%이상이 되면 오히려 불순물로 작용하여 DLC 박막의 Stress는 급격히 증가하고 마찰계수도 높아짐을 알 수 있다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.44-44
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• 2011

현존하는 초경도 박막물질 중 입방정 질화붕소(cBN)은 철계 금속과의 반응안정성 및 낮은 온도에서의 합성가능성 등 많은 장점을 가지고 있다. 그러나 필수로 수반되는 이온충돌 효과로 인해 박막 내 높은 잔류응력으로 인한 박리 현상으로 응용이 어려운 실정에 있다. 현재까지 이를 개선하기 위해 수소를 첨가하여 박막의 잔류응력을 줄이는 연구, B4C 타겟을 이용하여 B-C-N 의 gradient layer를 설계하여 점진적으로 잔류응력을 감소시키는 연구 등 많은 연구들이 진행되고 있다. 본 연구에서는 MOCVD로 만들어진 NCD(Nano Crystalline Diamond) buffer layer 위에 RF-UBM(unbalanced magnetron) PVD를 이용하여 BN을 증착시켰다. hBN 타겟을 이용하여 2mTorr에서 400W 의 RF 파워를 사용하여 기판에 RF bias를 인가해 실험하였다. cBN 박막과 기판의 lattice mismatch 를 줄이기 위해서 본 연구소에서 제공되는 NCD 기판을 사용하였으며, 다이아몬드 기판과 cBN 박막의 1:1 에피성장을 이루기 위해 상온에서부터 800도까지 온도 변화를 주어 cBN을 증착시켰다. FTIR(Fourier transform infrared spectroscopy)로 $sp^2$구조인 hBN과 $sp^3$구조인 cBN의 성장유무를 확인하였으며, FTIR peak intensity 차이로 박막내 cBN의 함량을 계산하였고, Scratch test로 박막과 기판사이의 밀착력을 상대적으로 비교하였으며, 격자의 에픽성장을 확인하기 위해 FIB 의 작업을 거쳐 HRTEM 으로 각 위치별로 SAD pattern를 이용하여 성장거동을 확인하였다.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.185-189
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• 2005

We reported here nano-scale electrical phase-change recording in amorphous $Ge_2Sb_2Te_5$ media using an atomic force microscope (AFM) having conducting probes. In recording process, a pulse voltage is applied to the conductive probe that touches the media surface to change locally the electrical resistivity of a film. However, in contact operation, tip/media wear and contamination could major obstacles, which degraded SNR, reproducibility, and lifetime. In order to overcome tip/media wear and contamination in contact mode operation, we adopted the W incorporated diamond-like carbon (W-DLC) films as a protective layer. Optimized mutilayer media were prepared by a hybrid deposition system of PECVD and RF magnetron sputtering. When suitable electrical pulses were applied to media through the conducting probe, it was observed that data bits as small as 25 nm in diameter have been written and read with good reproducibility, which corresponds to a data density of $1 Tbit/inch^2$. We concluded that stable electrical phase-change recording was possible mainly due to W-DLC layer, which played a role not only capping layer but also resistive layer.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.141-141
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• 2011

DLC(Diamond Like Carbon) 박막은 높은 경도, 낮은 마찰계수, 내화학성 등의 우수한 트라이볼로지적 특성을 가지고 있기 때문에 다양한 산업분야에서 적용되고 있다. 이러한 DLC 박막은 합성기구나 구조의 관점에서 몇 가지 다른 이름으로 불려지기도 한다. 밀도와 경도가 높기 때문에 경질탄소(Hard Carbon)라고도 불려지며, 수소를 함유한 경우에는 수소함유 비정질 탄소(Hydrogenated Amorphous Carbon)이라는 이름이 사용되며, 고밀도 탄소(Dense Carbon) 또는 고밀도 탄화수소(Dense Hydrocarbon)라고 불리기도 한다. 이렇듯 DLC 박막은 합성방법에 따라 함유된 수소와 탄소의 결합구조의 차이가 있다. 수소 함유한 DLC 박막은 20~50%까지 수소를 함유하며, DLC막의 기계적, 광학적, 전기적 특성들이 수소함량과 밀접한 관계를 가지고 있는 것으로 알려져 있다. 그러나 함유된 수소가 $300^{\circ}C$ 이상의 온도에서는 쉽게 결합에서 이탈되면서 흑연화와 더불어 마찰마모시 코팅층의 파손이 발생한다고 보고되고 있고, 또한 수소량이 증가함에 따라 DLC 박막의 경도는 감소하게 되는데, 이는 수소에 의해 dangling bond가 Passivation되면 탄화수소의 3차원적인 Crosslinking은 그만큼 감소하게 되기 때문이라고 알려져 있다. 본 연구에서는 PECVD를 이용하여 여러 가지 공정에 따른 DLC 박막을 증착시켰으며, 수소함유량에 따른 DLC막의 구조와 그에 따른 경도 변화를 살펴보았다. FTIR(Furier Transform Infrared Spectroscopy)과 Raman Spectroscopy을 이용하여 DLC막의 수소의 결합상태를 관찰하였으며, Nano Indentation을 사용하여 미소경도를 측정하였고, FE-SEM을 이용하여 표면과 단면을 관찰하였다. 막의 두께 측정에는 ${\alpha}$-Step을 사용하였으며, Ball-on-Disk 타입의 Tribo-meter을 이용하여, 모재의 경도에 따른 마찰계수 변화를 관찰하였다.

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.357-364
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• 2021

In this study, DLC films deposited by PECVD were evaluated to the properties of super-hydrophobic by CF₄ treatment. The structure of DLC films were confirmed by Raman Spectra whether or not mixed sp³ (like diamond) peak and sp² (like graphite) peak. And the hydrogen contents in the DLC films (F-DLC) were measured by RBS analysis. In addition, DLC films were analyzed by scratch test for adhesion, nano-indentation for hardness and tribo-meter of Ball-on-disc type for friction coefficient. In the result of analysis, DLC films had traditional structure regardless of variation of hardness at constant conditions. Also adhesion of DLC film was increased as higher material hardness. Otherwise, friction coefficient was increased as lower material hardness. The DLC films were treated by CF₄ plasma treatment to enhance the properties of super-hydrophobic. And the DLC films were measured by ESEM(Enviromental Scanning Electron Microscope) for water condensation.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.4
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• pp.155-160
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• 2019

Diamond Like Carbon (DLC) is a metastable form of amorphous carbon that have superior material properties such as high mechanical hardness, chemical inertness, abrasion resistance, and biocompatibility. Furthermore, its material properties can be tuned by additional doping such as nitrogen or boron. However, either pure DLC or doped DLC show poor adhesion property that makes it difficult to apply contact processing technique. Therefore we propose ultrafast laser micromachining which is non-contact precision process without mechanical degradation. In this study, we developed precision machining process of DLC thin film using an ultrafast laser by investigating the process window in terms of laser fluence and laser wavelength. We have also demonstrated various patterns on the film without generating any microcracks and debris.

• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.372-376
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• 2009

In the modern semiconductor industry, lithography process is used to construct specific patterns. However, due to the decreasing of line width, these days, more and more researchers are interested in PMMA(Poly Methyl Methacrylate) lithography by using e-beam instead of the prior method, PR(Photoresist) lithography by using UV(Ultra-Violet). Additionally, the patterns constructed by lithography are collapsed during the process of cleansing remnants and the resistance against the breakdown of the patterns is known to be proportional to the elastic modulus of pattern-constructing materials. In this research, we measured the change of hardness and elastic modulus of PMMA film surface according to the change of time spent to soft-bake the PMMA film. During the measurement, we controlled the tip pressure from $25{\mu}N$ to $8,500{\mu}N$ having intervals that are $134.52{\mu}N$. For these measurements, we used the Triboindenter from Hysitron to gauge the hardness and elastic modulus and the tip we used was Berkovich diamond Tip.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1507-1510
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• 2005

This study was carried out as a part of the research on the development of a maskless and electroless process for fabricating metal micro/nanostructures by using a nanoindenter and an electroless deposition technique. $2-\mu{m}-deep$ indentation tests on Ni and Cu samples were performed. The elastic recovery of the Ni and Cu was 9.30% and 9.53% of the maximum penetration depth, respectively. The hardness and the elastic modulus were 1.56 GPa and 120 GPa for Ni and 1.49 GPa and 100 GPa for Cu. The effect of single-point diamond machining conditions such as the Berkovich tip orientation (0, 45, and $90^{\circ}$) and the normal load (0.1, 0.3, 0.5, 1, 3, and 5 mN), on both the deformation behavior and the morphology of cutting traces (such as width and depth) was investigated by constant-load scratch tests. The tip orientation had a significant influence on the coefficient of friction, which varied from 0.52-0.66 for Ni and from 0.46-0.61 for Cu. The crisscross-pattern sample showed that the tip orientation strongly affects the surface quality of the machined area during scratching. A selective deposition of Cu at the pit-like defect on a p-type Si(111) surface was also investigated. Preferential deposition of the Cu occurred at the surface defect sites of silicon wafers, indicating that those defect sites act as active sites for the deposition reaction. The shape of the Cu-deposited area was almost the same as that of the residual stress field.

• Tribology and Lubricants
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• v.33 no.3
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• pp.106-111
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• 2017

Sapphire is an anisotropic material with excellent physical and chemical properties and is used as a substrate material in various fields such as LED (light emitting diode), power semiconductor, superconductor, sensor, and optical devices. Sapphire is processed into the final substrate through multi-wire saw, double-side lapping, heat treatment, diamond mechanical polishing, and chemical mechanical polishing. Among these, chemical mechanical polishing is the key process that determines the final surface quality of the substrate. Recent studies have reported that the material removal characteristics during chemical mechanical polishing changes according to the crystal orientations, however, detailed analysis of this phenomenon has not reported. In this work, we carried out chemical mechanical polishing of C(0001), R($1{\bar{1}}02$), and A($11{\bar{2}}0$) substrates with different sapphire crystal planes, and analyzed the effect of crystal orientation on the material removal characteristics and their correlations. We measured the material removal rate and frictional force to determine the material removal phenomenon, and performed nano-indentation to evaluate the material characteristics before and after the reaction. Our findings show that the material removal rate and frictional force depend on the crystal orientation, and the chemical reaction between the sapphire substrate and the slurry accelerates the material removal rate during chemical mechanical polishing.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.559-569
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• 2010

The liquid-phase sintering method was used to prepare a glass lens forming core composed of SiC-$Al_2O_3-Y_2O_3$. Spark plasma sintering was used to obtain dense sintered bodies. The sintering characteristics of different SiC sources and compositions of additives were studied. Results revealed that, owing to its initial larger surface area, $\alpha$-SiC offers sinterability that is superior to that of $\beta$-SiC. A maximum density of $3.32\;g/cm^3$ (theoretical density [TD] of 99.7%) was obtained in $\alpha$-SiC-10 wt% ($6Al_2O_3-4Y_2O_3$) sintered at $1850^{\circ}C$ without high-energy ball milling. The maximum hardness and compression stress of the sintered body reached 2870 Hv and 1110 MPa, respectively. The optimum ultra-precision machining parameters were a grinding speed of 1243 m/min, work spindle rotation rate of 100 rpm, feed rate of 0.5 mm/min, and depth of cut of $0.2\;{\mu}m$. The surface roughnesses of the thus prepared final products were Ra = 4.3 nm and Rt = 55.3 nm for the aspheric lens forming core and Ra = 4.4 nm and Rt = 41.9 for the spherical lens forming core. These values were found to be sufficiently low, and the cores showed good compatibility between SiC and the diamond-like carbon (DLC) coating material. Thus, these glass lens forming cores have great potential for application in the lens industry.