• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.336-339
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• 2002

For the improvement of the lock-in frequency of a ring laser gyro, a low-scattering mirror was employed in the laser resonator. A super-polishing technique produced fine mirror substrates of less than 1-A-rms-roughness. The mirror coating using an ionbeam sputtering technique reduced the scattering loss to less than 30 ppm. As a result of the mirror scattering enhancement of the ring laser, the lock-in frequency of the gyro was improved up to about 0.1 deg/sec.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.29-35
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• 1998

Substrates, SiC raw materials and graphite crucibles were purified for growing the high quality 6H-SiC single crystal ingot. Especially, XRD data of raw materials were analyzed before and after purification. We have grown 6H-SiC single crystal ingot up to 33 mm in diameter and 11 mm in length and SiC wafer for using the substrate and observing the internal defects was about 33 mm in diameter and 0.5 mm in thickness. Utilizing optical microscpe and Raman spectroscopy, internal defects density and crystallinity of the SiC wafer obtained by purification processes before crystal growth were measured. As a result, micropipe density and planar defect density were 100/$\textrm{cm}^2$ and 30/$\textrm{cm}^2$ respectively. Therefore, high quality 6H-SiC single crystal could be grown because internal defects density of 6H-SiC single crystal ingot was decreased by the purification processes before crystal growth.

• Tribology and Lubricants
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• v.32 no.4
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• pp.119-124
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• 2016

In the sapphire wafering process, lapping is a crucial operation in order to reduce the damaged layer and achieve the target thickness. Many parameters, such as pressure, velocity, abrasive, slurry and plate, affect lapping characteristics. This paper presents an experimental investigation on the effect of the plate groove on the material removal rate and roughness of the wafer. We select the spiral pattern and rectangular type as the groove shapes. We vary the groove density by controlling the groove shape dimension, i.e., the groove width and pitch. As the groove density increases to 0.4, the material removal rate increases and gradually reaches a saturation point. When the groove density is low, the pressing load is mostly supported by the thick film, and only a small amount acts on the abrasives resulting to a low material removal rate. The roughness decreases on increasing the groove density up to 0.3 because thick film makes partial participations of large abrasives which make deep scratches. From these results, we could conclude that the groove affects the contact condition between the wafer and plate. At the same groove density, the pitch has more influence on reducing the film thickness than the groove width. By decreasing the groove density with a smaller pitch and larger groove width, we could achieve a high material removal rate and low roughness. These results would be helpful in understanding the groove effects and determining the appropriate groove design.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.86-92
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• 2013

$SF_6/O_2$ inductively coupled plasmas were employed to texture Si surface as a pretreatment for nanocrystalline diamond film growth. It was found that the $SF_6/O_2$ plasma texturing provided a very wide process window where normalized roughness values in the range of 2~16 could be obtained. Significantly improved nucleation densities of ${\sim}6.5{\times}10^{10}cm^{-2}$ compared to conventional mechanical abrasion were achieved after seeding for the textured Si substrate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.165-165
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• 2007

투명전도박막은 ITO, $SnO_2$, ZnO, 등이 있으나 $SnO_2$는 자외선 영역까지 투과시키는 우수한 광학적 특성을 나타내지만, 상당히 큰 전기저항으로 인해 현재는 현재 ITO가 널리 이용되고 있다. ITO(Indium Tin Oxide)박막은 자외선 영역에서 반사율이 높으며 가시광선영역에서는 80%이상의 뛰어난 투과율을 가지고 있다. 또한 낮은 전기저항과 넓은 광학적 밴드갭 때문에 가장 유용한 투과전도성 재료 중에 하나이다. 이러한 특성 때문에 여러 가지 문자 표시소자의 투명전극, 태양전지의 창재료, 정전차폐를 위한 반도체 포장재료, 열반사막, 면발열체, 광전변환 소자에 응용되고 있다. 일반적으로 박막의 제작에는 저항가열법과 전자선가열법, 스퍼터링법의 물리적 증착과 화학적 증착으로 나뉜다. 본 논문에서는 증착온도를 달리 하여 RF-sputtering에 의해 ITO박막을 증착한 후 온도증가에 따른 박막의 특성을 연구하였으며 또한 광역평탄화를 위한 CMP공정을 적용하여 증착온도가 연마에 미치는 영향을 연구하였다. 본 실험에서 사용된 ITO박막은 $2{\times}2Cm$의 Corning glass위에 증착되었으며 타겟은 $In_2O_3$와 $SnO_2$가 9:1로 혼합된 Purity 99.99%이상의 직경 2 inch인 ITO타겟을 사용하였다. 박막 증착시 기판온도는 상온에M $200^{\circ}C$까지 변화시켰으며 RF power는 100W로 일정하게 하였으며 증착압력은 $8{\times}10^{-2}$Torr이였다. CMP공정조건은 헤드속도 60rpm, 플레이튼 속도 60rpm, 슬러리 주입 유량 60mml/min, 압력 $300g/cm^2$이였다. 전기적 특성은 four point probe를 이용하여 측정하였으며 광학적 특성은 UV-Visible Spectrometer를 이용하여 200~900nm의 파장범위에서 광투과도를 측정하였다.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.9
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• pp.32-37
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• 2008

Freestanding hydride vapor phase epitaxy grown GaN(Gallium Nitride) substrates subjected to various polishing methods were characterized for their surface and subsurface conditions, Although CMP(Chemical Mechanical Polishing) is one of the best approaches for reducing scratches and subsurface damages, the removal rate of Ga-polar surface in CMP is insignificant($0.1{\sim}0.3{\mu}m$/hr) as compared with that of N-polar surface, Therefore, conventional MP(Mechanical Polishing) is commonly used in the GaN substrate fabrication process, MP of (0001) surface of GaN has been demonstrated using diamond slurries with different abrasive sizes, Diamond abrasives of size ranging from 30nm to 100nm were dispersed in ethylene glycol solutions and mineral oil solutions, respectively. Significant change in the surface roughness ($R_a$ 0.15nm) and scratch-free surface were obtained by diamond slurry of 30nm in mean abrasive size dispersed in mineral oil solutions. However, MP process introduced subsurface damages confirmed by TEM (Transmission Electronic Microscope) and PL(Photo-Luminescence) analysis.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.795-797
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• 2010

습식 식각은 식각용액으로서 화학용액을 사용하는 공정으로 반응물이 기판표면에서 화학반응을 일으켜 표면을 식각하는 과정이며, 표면결합의 제거를 위한 식각연마와 폴리싱을 위한 식각, 그리고 구조적 형상 패턴등이 있다. 여기서 화학용액은 산화제 또는 환원제 역할을 하는 혼합용액으로 구성된다. 습식 식각 시 수${\mu}m$의 해상도를 얻기 위해서는 그 부식액의 조성이나, 에칭시간, 부식액의 온도 등을 고려하여야 한다. 또한 습식 식각 후 포토 레지스트를 제거하는 과정에서 포토 레지스트를 깨끗이 제거해야 하며, 제거공정 자체가 a-Si:H 박막을 부식 하지 않을 조건으로 행하여야 한다. 포토레지스트 제거 후 잔류 포토 레지스트를 제거하기 위해서 본 실험에서는 RCA-I 세척 기법을 사용한 후 D.I 로 린스 하였다. 본 실험에서 사용한 금속은 Cr, Al, ITO 로 모두 DC sputter 방법을 사용해서 증착하여 사용하였다. Cr박막은 $1300\AA$ 정도의 두께를 사용하였고, ITO (Indium Tin Oxide) 박막은 가시광 영역에서 투명하고 (80% 이상의 transmittance), 저저항 (Sheet Resistance : $50{\Omega}/sq$ 이하) 인 박막을 사용하였으며, 신호선으로 주로 사용되는 Al등의 증착조건에 따른 wet etching 특성을 조사하였다.

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.466-472
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• 2008

Purple Gold is the alloy consisting of 78wt%Au-22wt%Al, and is expressed as a chemical formula, $AuAl_2$. Lately it is being used for the material of accessories or the decorative ornaments, being one of the colored golds having the peculiar purple color, like White Gold and Pink Gold. Purple Gold has the weak point in shaping through casting process due to the bad malleability and castability, being the intermetalic compound of Au and Al. Therefore, it is possible to produce the final product only by the cutting and the grinding process or to use it as a decorative coat with the thin film evaporation. This study implemented two kinds of thin film experiments. One is the case that heat treatment was made after Au and Al deposition evaporated separately with a weight ratio 78:22 on the 200nm$SiO_2$/Si substrate. The other is the case that the surface deposition was made through the vacuum evaporation, keeping the glass substrate temperature remain room temperature, using the bulk $AuAl_2$ as a source. The final film property was measured, focusing on the Purple Gold's color and thickness through the bare eye inspection, the microstructure analysis, the surface resistance analysis, the color difference analysis, and XRD analysis. Purple Gold was not formed, as the excessive surface agglomeration occurred, in case of being produced and treated thermally with 12.5nmAu/40nmAl/200nm$SiO_2$/Si structure. Our results suggest that of Purple Gold films, showing the same purple color as the bulk's, were successfully deposited with the direct thermal evaporation from the $AuAl_2$ bulk source.

• Resources Recycling
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• v.31 no.6
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• pp.60-65
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• 2022

This study presents the carburization process for recycling sludge, which was formed during silicon wafer machining. The sludge used in the carburization process is a mixture of silicon and silicon carbide (SiC) with iron as an impurity, which originates from the machine. Additionally, the sludge contains cutting oil, a fluid with high viscosity. Therefore, the sludge was dried before carburization to remove organic matter. The dried sludge was washed by acid cleaning to remove the iron impurity and subsequently carburized by heat treatment under vacuum to form the SiC powder. The ratio of silicon to SiC in the sludge was varied depending on the sources and thus carbon content was adjusted by the ratio. With increasing SiC content, the carbon content required for SiC formation increased. It was demonstrated that substoichiometric SiC_x (x<1) was easily formed when the carbon content was insufficient. Therefore, excess carbon is required to obtain a pure SiC phase. Moreover, size reduction by high-energy milling had a beneficial effect on the suppression of SiC_x, forming the pure SiC phase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.776-780
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• 2015

In this paper, we have studied the effect of mechanical polishing to Ga-polar face for reducing the wafer bowing and strain in free-standing GaN. After the mechanical polishing to Ga-polar face, the bowing of the free-standing GaN substrate significantly decreased with increasing the size of diamond slurry, and eventually changed the bowing direction from concave to convex. Furthermore, the full width at half maximum (FWHM) of high-resolution X-ray diffraction (HR-XRD) were decreased, especially the FWHM of (1 0 2) reflection for $1.0{\mu}m$ size of diamond slurry was significantly decreased from 630 to 203 arcsec. In the case, we confirmed that the compressive strain in Ga-polar face was fully released by Raman measurement.