• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.397-397
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• 2007

Multilayer transparent electrodes, having a much lower electrical resistance than the widely used transparent conducting oxide electrodes, were prepared by using radio frequency magnetron sputtering. The multilayer structure consisted of five layers, indium tin oxided(ITO)/zinc oxide(ZnO)/Ag/oxide(ZnO)/ITO. With about 50nm thick ITO films, the multilayer showed a high optical transmittance in the visible range of the spectrum and had color neutrality. The electrical and optical properties of ITO/ZnO/Ag/ZnO/ITO multilayer were changed mainly by Ag film properties, which were affected by the deposition process of the upper layer. Especially ZnO layer was improved to adhesion of Ag and ITO. A high quality transparent electrode, having a resistance as low as and a high optical transmittance of 91% at 550nm, was obtained. It could satisfy the requirement for the flexible OLED and LCD.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.4-4
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• 2008

The progress in flat panel displays over the last two decades has been astonishing. In just 20 years, the LCD-TV grew up from a 2-inch curiosity, to an industry that will sell about 120 million flat panel TV's this year, with viewing area up to 4000 times larger. That success is based on continuous innovation, especially in manufacturing processes. For the next decade to bring another doubling of the business, progress will need to continue in four major areas: Human factors, ecological impact, visual quality, and of course continued drive towards affordability. This talk will detail the technology advances that can allow this industry to meet those challenges. Human factors. Today, we adapt our lifestyle to our technology. People organize their offices, and their homes, around displays. We pass around mobile phones to share images, rather than experiencing them as a group. Billions of newspapers continue to be sold daily. Advances in flexible displays can lead to large portable displays. "New era projection" includes the handheld Pico Projectors that are already on the market, and will ultimately appear integrated in mobile phones the same way cameras do today. "Eco" impact. Today TV's are one of the top energy consumers in a U.S. home, and the fastest growing. Watching a large flat panel TV can cost twice as much as running a large refrigerator. With today's concern about energy consumption, regulations are starting to emerge worldwide to limit TV electrical use. Fortunately, good solutions exist in using light management films to eliminate bulbs, saving power without increasing cost. Going forward, LED backlights will drive another step downward. OLED displays might be the ultimate solution. Visual quality. The color of an LCD-TV is still often considered inferior to a far less expensive CRT. And almost all displays suffer from representing a three-dimensional world on a two dimensional surface. The technology to improve color is available today, and will likely move from premium sets into the mainstream as costs come down. 3D is now arriving in movie theaters worldwide, and that will drive up the demand for similar realistic images in home theaters. And the technology is emerging today for 3D representation to move beyond specialized applications into everyday use, on screens large and small. Affordability. The world takes cost-down miracles for granted in consumer electronics. Each of these other advances will be balanced with a drive for affordability, especially as the market grows in emerging countries. The other three challenges must be met without increasing cost. Putting this all together, the next few years will emphasize "eco friendly" designs, and enhanced images such as 3D. By 2013 we will start to see serious penetration by emissive technologies (OLED, high efficiency plasma, or other), with the "ultimate display" likely not in the market for a decade. Lots of opportunities for innovation remain ahead of us.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.577-582
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• 2013

AZO (aluminum-doped zinc oxide) is one of the best candidate materials to replace ITO (indium tin oxide) for TCOs (transparent conductive oxides) used in flat panel displays, organic light-emitting diodes (OLEDs), and organic solar cells (OSCs). In the present study, to apply an AZO thin film to the transparent electrode of an organic solar cell, a low-temperature selective atomic layer deposition (ALD) process was adopted to deposit an AZO thin film on a flexible poly-ethylene-naphthalate (PEN) substrate. The reactive gases for the ALD process were di-ethyl-zinc (DEZ) and tri-methyl-aluminum (TMA) as precursors and H2O as an oxidant. The structural, electrical, and optical characteristics of the AZO thin film were evaluated. From the measured results of the electrical and optical characteristics of the AZO thin films deposited on the PEN substrates by ALD, it was shown that the AZO thin film appeared to be comparable to a commercially used ITO thin film, which confirmed the feasibility of AZO as a TCO for flexible organic solar cells in the near future.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.344-349
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• 2015

A new information society of late has arrived by the rapid development of various information & communications technologies. Accordingly, mobile devices which are light and thin, easy and convenient to carry on the market. Also, the requirements for the larger television sets such as fast response speed, low-cost electric power, wider visual angle display are sufficiently satisfied. The currently most widely studied display material, the Organic Light-emitting Diodes(OLEDs) overwhelms the Liquid Crystal Display(LCD), the main occupier of the market. This new material features a response speed of more than a thousand times faster, no need of backlight, a low driving voltage, and no limit of view angle. And the OLEDs has high luminance efficiency and excellent durability and environment resistance, quite different from the inorganic LED light source. The OLEDs with simple device structure and easy produce can be manufactured in various shapes such as a point light source, a linear light source, a surface light source. This will surely dominate the market for the next generation lighting and display device. The new display utilizes not the glass substrate but the plastic one, resulting in the thin and flexible substrate that can be curved and flattened out as needed. In this paper, OLEDs device was produced by changing thickness of Teflon-AF of hole injection material layer. And as for the electrical properties, the four layer device of ITO/TPD/$Alq_3$/BCP/LiF/Al and the five layer device of ITO/Teflon AF/TPD/$Alq_3$/BCP/Lif/Al were studied experimentally.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.74-74
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• 2010

모바일 정보통신기기를 중심으로 전자패키지의 초소형화, 고집적화를 위해 플립칩 공법의 적용이 증가되고 있는 추세이다. 플립칩 패키징 접합소재로는 솔더, ICA(Isotropic Conductive Adhesive), ACA(Anisotropic Conductive Adhesive), NCA(Non Conductive Adhesive) 등과 같은 다양한 접합소재가 사용되고 있다. 최근에는 언더필을 사용하는 플립칩 공법보다 미세피치 대응성을 위해 NCP를 이용한 플립칩 공법에 대한 요구가 증가되고 있는데, NCP의 상용화를 위해서는 공정성과 함께 신뢰성 확보가 필요하다. 본 연구에서는 LDI(LCD drive IC) 모듈을 위한 COF(Chip-on-Film) 플립칩 패키징용 NCP 포뮬레이션을 개발하고 이를 적용한 COF 패키지의 신뢰성을 조사하였다. 테스트베드는 면적 $1.2{\times}0.9mm$, 두께 $470{\mu}m$, 접속피치 $25{\mu}m$의 Au범프가 형성된 플리칩 실리콘다이와 접속패드가 Sn으로 finish된 폴리이미드 재질의 flexible 기판을 사용하였다. NCP는 에폭시 레진과 산무수물계 경화제, 이미다졸계 촉매제를 사용하여 다양하게 포뮬레이션을 하였다. DSC(Differential Scanning Calorimeter), TGA(Thermogravimetric Analysis), DEA(Dielectric Analysis) 등의 열분석장비를 이용하여 NCP의 물성과 경화거동을 확인하였으며, 본딩 후에는 보이드를 평가하고 Peel 강도를 측정하였다. 최적의 공정으로 제작된 COF 패키지에 대한 HTS (High Temperature Stress), TC (Thermal Cycling), PCT (Pressure Cooker Test)등의 신뢰성 시험을 수행한 결과 양산 적용 가능 수준의 신뢰성을 갖는 것을 확인할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.10-10
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• 2010

가시광역에서 80% 이상의 높은 투과율과 전기전도성을 동시에 갖는 투명전도성 산화물(TCO) 박막은 LCD, PDP, OLED, 태양전지 등의 다양한 분야에 투명전극재료로서 사용되고 있다. 이들 TCO 박막은 Magnetron sputtering, Chemical vapor deposition, Pulse laser deposition, Ink jet등과 같은 다양한 방법으로 증착할 수 있지만, 대면적의 기판에 균일한 박막형성 및 박막과 기판의 높은 부착력등 양산성의 관점에서 우월성을 가지고 있기 때문에 생산라인에서는 DC magnetron sputtering법이 주로 사용되고 있다. 이 경우, 산화물 박막의 미세구조, 내부응력, 광학적 및 전기적 특성은 스퍼터링 과정에서 발생하는 고에너지 입자들의 기판입사 충격에 크게 의존하기 때문에 고품질의 TCO박막을 제작하기 위해서는 증착공정인자들의 제어는 매우 중요한 것으로 알려져 있다. 대표적 TCO박막재료로서 $In_2O_3$계, ZnO계 및 $SnO_2$계를 들 수 있으며, 이들 중에서 Sn을 $In_2O_3$에 치환고용시킨 ITO박막의 경우, 전기적 및 광학적 특성이 상대적으로 우수하기 때문에 실용화 TCO박막으로서 가장 널리 사용되고 있다. 한편, Flexible display의 경우, 유연성의 폴리머기판위에 증착되는 TCO박막에 대하여 요구되는 특성으로는 높은 투과율 및 낮은 비저항은 물론, 박막표면의 평활도 (낮은 표면조도), bending에 대한 높은 기계적 특성 (낮은 내부응력), 수분침투에 대한 높은 barrier특성 및 저온공정 등을 들 수 있다. 그러나 높은 전기전도도를 가지는 ITO박막을 제작하기 위해서는 $200^{\circ}C$ 이상의 증착온도가 필요하며, 이때 얻어진 다결정의 ITO박막은 높은 표면조도 및 bending시에 낮은 기계적 내구성이 문제점으로 지적되고 있다. 한편, 기판가열 없이 증착한 비정질 ITO박막은 낮은 표면조도, 높은 엣칭속도 및 양호한 식각특성을 나타내지만, 상대적으로 높은 비저항 및 기판과의 낮은 부착력 등이 지적되고 있다. 따라서 본 강연에서는 비정질 ITO박막의 결정화 온도 (약 $160^{\circ}C$) 이상에서도 비정질 구조를 유지하기 때문에 낮은 표면조도와 높은 엣칭속도를 가지면서 상대적으로 전기적 특성과 기계적 내구성이 개선된 새로운 고온형 비정질 TCO박막에 대한 최근의 연구성과를 소개하고자 한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.398-398
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• 2007

The Liquid Crystal (LC) alignment uniformity is very important in LC devices. The alignment mechanism of LC molecules on a rubbed polyimide (PI) surface is very important for both LC fundamental research and application. So, Generally a rubbing method to align LC has been widely used to mass-produce LCD panels. But because rubbing method is contact method between rubbing fabric and indium-tin-oxide glass or flexible substrate, rubbing method has some defects, such as the electrode charges and the creation of contaminating particles. Thus we strongly recommend a non-contact alignment technique for getting rid of some defects of rubbing method. Most recently, the LC aligning capabilities achieved by ion-beam exposure on the organic and nonorganic thin film surface have been reported successfully. In this research, we studied the tilt angle generation and electro-optical performances for a NLC on homeotropic polyimide surfaces with ion-beam exposure. The LC aligning capabilities of a nematic liquid crystal (NLC) on a homeotropic PI surface using a new ion-beam method were studied. On the homeotropic PI surface, the tilt angle of the NLC by exposure ion-beam had a tendency to decrease as increased ion-beam energy density. And, on the homeotropic PI surface, the alignment character of the NLC with respect to ion-beam energy was good. And we achieved satisfactory result for EO character.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.263-270
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• 2018

Recently, porous ceramic materials with anti-static performance are urgently needed for semiconductor and OLED/LCD display manufacturing industry. In this work, we fabricated porous titanium manganese oxide ceramics having the surface resistivity of $10^8-10^{10}$ ohm and enhanced mechanical strength by partial sintering method using nanosized titanium oxide. By addition of nano-sized titanium oxide in the matrix, neck formation between grains was strengthened, which remarkably increased flexural strength up to 170 MPa (@porosity: 15 %), 110 MPa (@porosity: 31 %), compared to 80 MPa (@porosity: 26 %) for pristine titanium manganese oxide ceramics. We evaluated the performances of our ceramics as air-floating module for OLED flexible display manufacturing devices.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.53.2-53.2
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• 2010

지금까지 능동 구동 디스플레이의 TFT backplane에 사용하고 있는 채널 물질로는 수소화된 비정질 실리콘(a-Si:H)과 저온 폴리실리콘(low temperature poly-Si)이 대표적이다. 수소화된 비정질 실리콘은 TFT-LCD 제조에 주로 사용되는 물질로 제조 공정이 비교적 간단하고 안정적이며, 생산 비용이 낮고, 소자 간 특성이 균일하여 대면적 디스플레이 제조에 유리하다. 그러나 a-Si:H TFT의 이동도(mobility)가 1 cm2/Vs이하로 낮아 Full HD 이상의 대화면, 고해상도, 고속 동작을 요구하는 UD(ultra definition)급 디스플레이를 개발하는데 있어 한계 상황에 다다르고 있다. 또한 광 누설 전류(photo leakage current)의 발생을 억제하기 위해서 화소의 개구율(aperture ratio)을 감소시켜야하므로 패널의 투과율이 저하되고, 게이트 전극에 지속적으로 바이어스를 인가 시 TFT의 문턱전압(threshold voltage)이 열화되는 문제점을 가지고 있다. 문제점을 극복하기 위한 대안으로 근래 투명 산화물 반도체(transparent oxide semiconductor)가 많은 관심을 얻고 있다. 투명 산화물 반도체는 3 eV 이상의 높은 밴드갭(band-gap)을 가지고 있어 광 흡수도가 낮아 투명하고, 광 누설 전류의 영향이 작아 화소 설계시 유리하다. 최근 다양한 조성의 산화물 반도체들이 TFT 채널 층으로의 적용을 목적으로 활발하게 연구되고 있으며 ZnO, SnO2, In2O3, IGO(indium-gallium oxide), a-ZTO(amorphous zinc-tin-oxide), a-IZO (amorphous indium-zinc oxide), a-IGZO(amorphous indium-galliumzinc oxide) 등이 그 예이다. 이들은 상온 또는 $200^{\circ}C$ 이하의 낮은 온도에서 PLD(pulsed laser deposition)나 스퍼터링(sputtering)과 같은 물리적 기상 증착법(physical vapor deposition)으로 손쉽게 증착이 가능하다. 특히 이중에서도 a-IGZO는 비정질임에도 불구하고 이동도가 $10\;cm2/V{\cdot}s$ 정도로 a-Si:H에 비해 월등히 높은 이동도를 나타낸다. 이와 같이 a-IGZO는 비정질이 가지는 균일한 특성과 양호한 이동도로 인하여 대화면, 고속, 고화질의 평판 디스플레이용 TFT 제작에 적합하고, 뿐만 아니라 공정 온도가 낮은 장점으로 인해 플렉시블 디스플레이(flexible display)의 backplane 소재로서도 연구되고 있다. 본 실험에서는 rf sputtering을 이용하여 증착한 a-IGZO 박막에 대하여 열처리 조건 변화에 따른 a-IGZO 박막들의 광학적, 전기적 특성변화를 살펴보았고, 이와 더불어 a-IGZO 박막을 TFT에 적용하여 소자의 특성을 분석함으로써, 열처리에 따른 Transfer Curve에서의 우리가 요구하는 Threshold Voltage(Vth)의 변화를 관찰하였다.