• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.475-480
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• 2017

In this paper, the conductivity of the fine pattern is improved in the insulating substrate by laser-induced forward transfer (LIFT) process. The high laser beam energy generated in conventional laser induced deposition processes induces problems such as low deposition density and oxidation of micro-patterns. These problems were improved by using a polymer coating layer for improved deposition accuracy and conductivity. Chromium and copper were used to deposit micro-patterns on silicon wafers. A multi-pulse laser beam was irradiated on a metal thin film to form a seed layer on an insulating substrate(SiO2) and electroless plating was applied on the seed layer to form a micro-pattern and structure. Irradiating the laser beam with multiple scanning method revealed that the energy of the laser beam improved the deposition density and the surface quality of the deposition layer and that the electric conductivity can be used as the microelectrode pattern. Measuring the resistivity after depositing the microelectrode by using the laser direct drawing method and electroless plating indicated that the resistivity of the microelectrode pattern was $6.4{\Omega}$, the resistance after plating was $2.6{\Omega}$, and the surface texture of the microelectrode pattern was uniformly deposited. Because the surface texture was uniform and densely deposited, the electrical conductivity was improved about three fold.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.2
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• pp.114-121
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• 2001

A circuit model for active-controlled field emitter array(ACFEA) as an electron source of active-controlled field emission display(ACFED) has been proposed. The ACFEA with hydrogenated amorphous silicon thin-film transistor(a-Si:H TFT) and Spindt-type molibdenum tips (Spindt-Mo FEA) has been fabricated monolithically on the same glass. A-Si:H TFT is used as a control device of field emitters, resulting in stabilizing emission current and lowering driving voltage. The basic model parameters extracted from the electrical characteristics of the fabricated a-Si:H TFT and Spindt-Mo FEA were implemented into the ACFEA model with a circuit simulator SPICE. The accuracy of the equivalent circuit model was verified by comparing the simulated results with the measured one through DC analysis of the ACFEA. The transient analysis of the ACFEA showed that the gate capacitance of FEA along with the drivability of TFT strongly affected the response time. With the fabricated ACFEA, we obtained a response time of 15$mutextrm{s}$, which was enough to make 4bit/color gray scale with the pulse width modulation (PWM).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.1
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• pp.20-26
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• 2001

Titanium boride ($\textrn{TiB}_{x}$) films were deposited on (100) silicon substrates at the substrate temperature of $500^{\circ}C$ by means of the co-evaporation of titanium and boron evaporants during deposition. The co-evaporation method makes it possible to deposit the non-stoichiometric films with different boron-to-titanium ratio($0{\le}B/Ti \le 2.5$). The resistivity increases linearly as the boron-to-titanium ratio in the as-deposited films is increased. The surface roughness of $\textrn{TiB}_{x}$ films is changed as a function of the boron-to-titanium ratio. The XRD spectrum for pure titanium film shows a highly (002) preferred orientation. For B/Ti=0.59 ratio only a single TiB phase that shows a (111) preferred orientation is observed. However, the $\textrn{TiB}_{x}$ phase with the hexagonal structure of the $AlB_2$(C32) type appears as the boron concentration increase, and only a single $\textrn{TiB}_{x}$ phase is observed for $B/Ti \ge 2.0$ ratio. The $\textrn{TiB}_{x}$/Si samples reveal a tensile stress (3~$20{\times}^9$dyn/$\textrm{cm}^2$) in the overall composition of the films, although the magnitude of the residual stresses is depended on the nominal B/Ti ratio.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1261-1262
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• 2008

Laser-based crystallization techniques are ideally-suited for forming high-quality crystalline Si films on active-matrix display backplanes, because the highly-localized energy deposition allows for transformation of the as-deposited a-Si without damaging high-temperature-intolerant glass and plastic substrates. However, certain significant and non-trivial attributes must be satisfied for a particular method and implementation to be considered manufacturing-worthy. The crystallization process step must yield a Si microstructure that permits fabrication of thin-film transistors with sufficient uniformity and performance for the intended application and, the realization and implementation of the method must meet specific requirements of viability, robustness and economy in order to be accepted in mass production environments. In recent years, Low Temperature Polycrystalline Silicon (LTPS) has demonstrated its advantages through successful implementation in the application spaces that include highly-integrated active-matrix liquid-crystal displays (AMLCDs), cost competitive AMLCDs, and most recently, active-matrix organic light-emitting diode displays (AMOLEDs). In the mobile display market segment, LTPS continues to gain market share, as consumers demand mobile devices with higher display performance, longer battery life and reduced form factor. LTPS-based mobile displays have clearly demonstrated significant advantages in this regard. While the benefits of LTPS for mobile phones are well recognized, other mobile electronic applications such as portable multimedia players, tablet computers, ultra-mobile personal computers and notebook computers also stand to benefit from the performance and potential cost advantages offered by LTPS. Recently, significant efforts have been made to enable robust and cost-effective LTPS backplane manufacturing for AMOLED displays. The majority of the technical focus has been placed on ensuring the formation of extremely uniform poly-Si films. Although current commercially available AMOLED displays are aimed primarily at mobile applications, it is expected that continued development of the technology will soon lead to larger display sizes. Since LTPS backplanes are essentially required for AMOLED displays, LTPS manufacturing technology must be ready to scale the high degree of uniformity beyond the small and medium displays sizes. It is imperative for the manufacturers of LTPS crystallization equipment to ensure that the widespread adoption of the technology is not hindered by limitations of performance, uniformity or display size. In our presentation, we plan to present the state of the art in light sources and beam delivery systems used in high-volume manufacturing laser crystallization equipment. We will show that excimer-laser-based crystallization technologies are currently meeting the stringent requirements of AMOLED display fabrication, and are well positioned to meet the future demands for manufacturing these displays as well.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.443-455
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• 2013

Electrochemical studies on charge transfer reactions across the interface between two immiscible electrolyte solutions (ITIES) have greatly attracted researcher's attentions due to their wide applicability in research fields such as ion sensing and biosensing, modeling of biomembranes, pharmacokinetics, phase-transfer catalysis, fuel generation and solar energy conversion. In particular, there have been extensive efforts made on developing sensing platforms for ionic species and biomolecules via gelifying one of the liquid phases to improve mechanical stability in addition to creating microscale interfaces to reduce ohmic loss. In this review, we will mainly discuss on the basic principles, applications and future aspects of various sensing platforms utilizing ion transfer reactions across the ITIES. The ITIES is classified into four types : (i) a conventional liquid/liquid interface, (ii) a micropipette supported liquid/liquid interface, (iii) a single microhole or an array of microholes supported liquid/ liquid interface on a thin polymer film, and (iv) a microhole array liquid/liquid interface on a silicon membrane. Research efforts on developing ion selective sensors for water pollutants as well as biomolecule sensors will be highlighted based on the use of direct and assisted ion transfer reactions across these different ITIES configurations.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.122-122
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• 1999

Graphite with its advantages of high thermal conductivity, low thermal expansion coefficient, and low elasticity, has been widely used as a structural material for high temperature. However, graphite can easily react with oxygen at even low temperature as 40$0^{\circ}C$, resulting in CO2 formation. In order to apply the graphite to high temperature structural material, therefore, it is necessary to improve its oxidation resistive property. Silicon Carbide (SiC) is a semiconductor material for high-temperature, radiation-resistant, and high power/high frequency electronic devices due to its excellent properties. Conventional chemical vapor deposited SiC films has also been widely used as a coating materials for structural applications because of its outstanding properties such as high thermal conductivity, high microhardness, good chemical resistant for oxidation. Therefore, SiC with similar thermal expansion coefficient as graphite is recently considered to be a g행 candidate material for protective coating operating at high temperature, corrosive, and high-wear environments. Due to large lattice mismatch (~50%), however, it was very difficult to grow thick SiC layer on graphite surface. In theis study, we have deposited thick SiC thin films on graphite substrates at temperature range of 700-85$0^{\circ}C$ using single molecular precursors by both thermal MOCVD and PEMOCVD methods for oxidation protection wear and tribological coating . Two organosilicon compounds such as diethylmethylsilane (EDMS), (Et)2SiH(CH3), and hexamethyldisilane (HMDS),(CH3)Si-Si(CH3)3, were utilized as single source precursors, and hydrogen and Ar were used as a bubbler and carrier gas. Polycrystalline cubic SiC protective layers in [110] direction were successfully grown on graphite substrates at temperature as low as 80$0^{\circ}C$ from HMDS by PEMOCVD. In the case of thermal MOCVD, on the other hand, only amorphous SiC layers were obtained with either HMDS or DMS at 85$0^{\circ}C$. We compared the difference of crystal quality and physical properties of the PEMOCVD was highly effective process in improving the characteristics of the a SiC protective layers grown by thermal MOCVD and PEMOCVD method and confirmed that PEMOCVD was highly effective process in improving the characteristics of the SiC layer properties compared to those grown by thermal MOCVD. The as-grown samples were characterized in situ with OES and RGA and ex situ with XRD, XPS, and SEM. The mechanical and oxidation-resistant properties have been checked. The optimum SiC film was obtained at 85$0^{\circ}C$ and RF power of 200W. The maximum deposition rate and microhardness are 2$mu extrm{m}$/h and 4,336kg/mm2 Hv, respectively. The hardness was strongly influenced with the stoichiometry of SiC protective layers.

• Journal of the Korean Society of Radiology
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• v.1 no.1
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• pp.11-16
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• 2007

In this study, we have performed contrast-detail analysis for an amorphous selenium(a-Se) based digital X-ray imaging system by using a contrast-detail phantom(CDRAD 2.0) to test its low contrast performance. The X-ray imaging system utilizes an 500-mm-thick a-Se semiconductor X-ray absorber coated over an amorphous silicon(a-Si) TFT(thin-film transistor) detector matrix with a $139mm{\times}139mm$ pixel size and a $46.7cm{\times}46.7cm$ active area. In the measurement of contrast-detail curves we first acquired X-ray images of the CDRAD 2.0 phantom at given test conditions(i.e., 40, 50, 60, 70, 80 kVp, and 16 mA.s), and then evaluated the contrast-detail characteristics of the imaging system from each phantom image by using an image quality factor called the image-quality-figure-inverse(IQFinv). The IQFinv values for the imaging system gradually improved with the photon fluence, indicating the improvement of image visibility: 24.4, 35.3, 39.2, 41.5, and 43.4 at photon fluences of $1.8{\times}105$, $5.9{\times}105$, $11.3{\times}105$, $19.4{\times}105$, and $29.4{\times}105$ photons/$mm^2$, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.100-102
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• 2013

Magnetron-sputtering법을 사용하여 기존에 연구하였던 CrAlN (Cr 7：Al 3)박막에 Si를 첨가하여 Si의 함량 변화에 따라 미세구조와 화학적 결합상태, 온도저항계수(TCR) 및 산화저항의 영향과 기계적특성 개선을 통한 multi-functional heater resistor layer로써의 가능성을 연구하였다. CrAlSiN 박막의 Si 함량에 변화에 따라 온도저항계수 변화를 확인하였으며 X-선 회절 분석(XRD) 패턴 분석결과 CrAlSiN 박막의 결정구조가 Bl-NaCl 구조를 가지고 있는 것을 확인하였으며 SEM과 AFM을 통한 표면 및 미세구조 분석결과 Si의 함량이 증가할수록 입자가 조밀해짐을 알 수 있었다. 최근 digital priting technology의 핵심 기술로 부각되고 있는 inkjet priting technology는 널리 태양전지뿐만 아니라 thin film process, lithography와 같은 반도체 공정 기술에 활용 할 수 있기 때문에 반도체 제조장비에도 사용되고 있으며, 현재 thermal inkjet 방식을 사용하고 있다. Inkjet printing technology는 전기 에너지를 잉크를 배출하기 위해 열에너지로 변환하는 thermal inkjet 방식을 사용하고 있는데, 이러한 thermal inkjet 방식은 기본적으로 전기저항이 필요하지만 electrical resistor layer는 잉크를 높은 온도에서 순간적으로 가열하기 때문에 부식이나 산화 등의 문제가 발생할 수 있어 이에 대한 보호층을 필요로 한다. 하지만, 고해상도, 고속 잉크젯 프린터, 대형 인쇄 등을 요구되고 있어 저 전력 중심의 잉크젯 프린터의 열효율을 방해하는 보호층 제거에 필요성이 제기되고 있다. 본 연구는 magnetron-sputtering을 사용하여 기존의 CrAlN 박막에 Si를 합성하여 anti-oxidation, corrosion resistance 그리고 low temperature coefficient of resistance 값을 갖는 multi-functional heater resistor layer로써 CrAlSiN 박막의 Si 함량에 따른 효과에 초점을 두었다. 본 실험은 CrAlN 박막에 Si 함량을 4~11 at%까지 첨가시켜 함량의 변화에 따른 특성변화를 확인하였다. 함량이 증가할수록 amorphous silicon nitride phase의 영향으로 박막의 roughness는 감소하였으며 XRD 분석결과 (111) peak의 Intensity가 감소함을 확인하였으며 SEM 관찰시 모든 박막이 columnar structure를 나타내었으며 Si함량이 증가할수록 입자가 치밀해짐을 보여주었다.Si함량이 증가할수록 CrAlN 박막에 비하여 면저항은 증가하였으며 TCR 측정결과 Si함량이 6.5 at%일 때 가장 안정한 TCR값을 나타내었다. Multi-functional heater resistor layer 역할을 하기 위해서, CrAlSiN 박막의 원소 분포, 표면 거칠기, 미세조직, 전기적 특성 등을 조사하였다. CrAlN 박막의 Si의 첨가는 크게 XRD 분석결과 주상 성장을 억제 할 수 있으며 SEM 분석을 통하여 Si 함량이 증가할수록 Si3N4 형성이 감소하며 입자크기가 작아짐을 확인하였다. 면저항의 경우 Si 함량이 증가함에 따라 높은 면저항을 나타내었으며 Si함량이 6.5 at%일 때 가장 낮은 TCR 값인 3120.53 ppm/K값을 보였다. 이 값은 상용되고 있는 heater resistor보다 높지만, CrAlSiN 박막이 더 우수한 기계적 특성을 가지고 있기 때문에 hybrid heater resistor로 적용할 수 있을 것으로 기대된다.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.384-391
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• 2005

A polymer optical microring resonator, which is laterally coupled to a straight bus waveguide, has been proposed and demonstrated using a nanoimprint technique. The propagation loss of the ring waveguide and the optical power coupling between the ring and bus waveguides was calculated by using a beam propagation method, then the dependence of the device performance on them was investigated using a transfer matrix method. We have especially introduced an imprint stamp incorporating a smoothing buffer layer made of a silicon nitride thin film. This layer played an efficient role in improving the sidewall roughness of the waveguide pattern engraved on the stamp and thus reducing the scattering loss. As a result the overall Q factor of the resonator was greatly increased. Also it reduced the gap between the ring and bus waveguides effectively to enhance the coupling between them, without relying on the direct writing method based on an e-beam writer. As for the achieved device performance at the wavelength of 1550 nm, the quality factor, the extinction ratio, and the free spectral range were ~103800, ~11 dB, and 1.16 m, respectively.

• The Magazine of the IEIE
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• v.29 no.6
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• pp.76-80
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• 2002

'Liquid Crystal의 상전이(相轉移)와 광학적 이방성(異方性)이 1888년과 1889년 F. Reinitzer와 O. Lehmann에 의해 Monatsch Chem.과 Z.Physikal.Chem.에 각각 보고된 후 부터 제2차 세계대전이 끝난 뒤인 1950년대 까지는 Liquid Crystal을 단지실험실에서의 기초학문 차원의 연구 대상으로만 다루어 왔다. 1963년 Williams가 Liquid Crystal Device로는 최초로 특허 출원을 하였으며, 1968년 RCA사의 Heilmeier등은 Nematic 액정(液晶)에 저주파(低周波) 전압(電壓)을 인가하면 투명한 액정이 혼탁(混濁)상태로 변화하는 '동적산란(動的散亂)'(Dynamic Scattering) 현상을 이용하여 최초의 DSM(Dynamic Scattering Mode) LCD(Liquid Crystal Display)를 발명하였다. 비록 150V 이상의 높은 구동전압과 과소비전력의 특성 때문에 실용화에는 실패하였지만 Guest-Host효과와 Memory효과 등을 발견하였다. 1970년대에 이르러 실온에서 안정되게 사용 가능한 액정물질들이 합성되고(H. Kelker에 의해 MBBA, G. Gray에 의한 Cyano-Biphenyl 액정의 합성), CMOS 트랜지스터의 발명, 투명도전막(ITO), 수은전지등의 주변기술들의 발전으로 인하여 LCD의 상품화가 본격적으로 이루어지게 되었다. 1971년에는 M. Shadt, W. Helfrich, J.L. Fergason등이 TN(Twisted Nematic) LCD를 발명하여 전자 계산기와 손목시계에 응용되었고, 1970년대 말에는 Sharp에서 Dot Matrix형의 휴대형 컴퓨터를 발매하였다. 이러한 단순 구동형의 TN LCD는 그래픽 정보를 표시하는 데에는 품질의 한계가 있어 1979년 영국의 Le Comber에 의해 a-Si TFT(amorphous Silicon Thin Film Transistor) LCD의 연구가 시작되었고, 1983년 T.J. Scheffer, J. Nehring, G. Waters에 의해 STN(Super Twisted Nematic) LCD가 창안되었고, 1980년 N. Clark, S. Lagerwall 및 1983년 K.Yossino에 의해 Ferroelectric LCD가 등장하여 LCD의 정보 표시량 증대에 크게 기여하였다. Color화의 진전은 1972년 A.G. Ficher의 셀 외부에 RGB(Red, Green, Blue) filter를 부착하는 방안과, 1981년 T. Uchida 등에 의한 셀 내부에 RGB filter를 부착하는 방법에 의해 상품화가 되었다. 1985년에는 J.L. Fergason에 의해 Polymer Dispersed LCD가 발명되었고, 1980년대 중반에 이르러 동화상(動畵像) 표시가 가능한 a-Si TFT LCD의 시제품(試製品) 개발이 이루어지고 1990년부터는 본격적인 양산 시대에 접어들게 되었다. 1990년대 초에는 STN LCD의 Color화 및 대형화(大型化) 고(高)품위화에 힘입어 Note-Book PC에 LCD가 본격적으로 적용이 되었고, 1990년대 후반에는TFT LCD의 표시품질 대비 가격경쟁력 확보로 인하여 Note-Book PC 시장을 독점하기에 이르렀다. 이후로는 TFT LCD의 대형화가 중요한 쟁점으로 부각되고 있고, 1995년 삼성전자는 당시 세계최대 크기의 22' TFT LCD를 개발하였다. 또한 LCD의 고정세(高情細)화를 위해 Poly Si TFT LCD의 개발이 이루어졌고, 디지타이져 일체형 LCD의 상품화가 그 응용의 폭을 넓혔으며, LCD의 대형화를 위해 1994년 Canon에 의해 14.8', 21' 등의 FLCD가 개발되었다. 대형화 방안으로 Tiled LCD 기술이 개발되고 있으며, 1995년에 Sharp에 의해 21' 두장의 Panel을 이어 붙인 28' TFT LCD가 전시되었고 1996년에는 21' 4장의 Panel을 이어 붙인 40'급 까지의 개발이 시도 되었으며 현재는 LCD의 특성향상과 생산설비의 성능개선과 안정적인 공정관리기술을 바탕으로 삼성전자에서 단패널 40' TFT LCD가 최근에 개발되었다. Projection용 디스플레이로는 Poly-Si TFT LCD를 이용하여 $25'{\sim}100'$사이의 배면투사형과 전면투사형 까지 개발되어 대형 TV시장을 주도하고 있다. 21세기 디지털방송 시대를 맞아 플라즈마디스플레이패널(PDP) TV, 액정표시장치 (LCD)TV, 강유전성액정(FLCD) TV 등 2005년에 약 1500만대 규모의 거대 시장을 형성할 것으로 예상되는 이른바 '벽걸이TV'로 불리는 차세대 초박형 TV 시장을 선점하기 위하여 세계 가전업계들이 양산에 총력을 기울이고 있다. 벽걸이TV 시장이 본격적으로 형성되더라도 PDP TV와 LCD TV가 직접적으로 시장에서 경쟁을 벌이는 일은 별로 없을 것으로 보인다. 향후 디지털TV 시장이 본격적으로 열리면 40인치 이하의 중대형 시장은 LCD TV가 주도하고 40인치 이상 대화면 시장은 PDP TV가 주도할 것으로 보는 시각이 지배적이기 때문이다. 그러나 이러한 직시형 중대형(重大型)디스플레이는 그 가격이 너무 높아서 현재의 브라운관 TV를 대체(代替)하기에는 시일이 많이 소요될 것으로 추정되고 있다. 그 대안(代案)으로는 비교적 저가격(低價格)이면서도 고품질의 디지털 화상구현이 가능한 고해상도 프로젝션 TV가 유력시되고 있다. 이러한 고해상도 프로젝션 TV용으로 DMD(Digital Micro-mirror Display), Poly-Si TFT LCD와 LCOS(Liquid Crystals on Silicon) 등의 상품화가 진행되고 있다. 인터넷과 정보통신 기술의 발달로 휴대형 디스플레이의 시장이 예상 외로 급성장하고 있으며, 요구되는 디스플레이의 품질도 단순한 문자표시에서 그치지 않고 고해상도의 그래픽 동화상 표시와 칼라 표시 및 3차원 화상표시까지 점차로 그 영역이 넓어지고 있다. <표 1>에서 보여주는 바와 같이 LCD의 시장규모는 적용분야 별로 지속적인 성장이 예상되며, 새로운 응용분야의 시장도 성장성을 어느 정도 예측할 수 있다. 따라서 LCD기술의 연구개발 방향은 크게 두가지로 분류할 수 있으며 첫째로는, 현재 양산되고 있는 LCD 상품의 경쟁력강화를 위하여 원가(原價) 절감(節減)과 표시품질을 향상시키는 것이며 둘째로는, 새로운 타입의 LCD를 개발하여 기존 상품을 대체하거나 새로운 시장을 창출하는 분야로 나눌 수 있다. 이와 같은 관점에서 현재 진행되고 있는 LCD기술개발은 다음과 같이 분류할 수 있다. 1) 원가 절감 2) 특성 향상 3) New Type LCD 개발.