• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1277-1280
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• 2005

A high-aspect-ratio and high-resolution stainless steel shadow mask for organic thin-film transistors (OTFTs) circuit has been fabricated by a new method which combines photochemical machining, micro-electrical discharge machining (micro-EDM), and electrochemical etching (ECE). First, connection lines and source-drain holes are roughly machined by photochemical etching, and then the part of source and drain holes is finished by the combination of micro-EDM and ECE processes. Using this method a $100\;\mu{m}$ thick stainless steel (AISI 304) shadow mask for inverter can be fabricated with the channel length of $30\;\mu{m}\;and\;10\;\mu{m}\;respectively.\;The\;width\;of\;connection line\;is\;150\;\mu{m}$. The aspect ratio of the wall is about 5 and 15, respectively. Metal lines and source-drain electrodes of OTFTs were successfully deposited through the fabricated shadow mask.

• 한국진공학회지
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• 제10권4호
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• pp.403-410
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• 2001

본 연구에서는 차세대 Cu 박막 증착 방법으로 유망한 CVD(chemical vapor deposition)방법으로 실질적 배선 증착 공정과 동일하게 시행하여 여러 조건에서 Cu를 증착하여 가장 EM에 관하여 높은 내구성을 가지는 조건을 알아보고 또한 박막의 미세구조가 EM에 어떠한 영향을 미치는지를 알아보았으며 MOCVD 방식으로 증착한 Cu박막의 표면과 barrier layer인 TiN과의 응력(stress)을 조사하여 차세대 EM모델인 grain boundary grooving 모델에 실질적으로 적용하였다. 또한, 이러한 실험을 행 한 후에 정확한 EM 현상을 관찰하고 분석하여 반도체 소자의 신뢰성과 성능개선, 결함 예측, 그리고 소자의 배선설계에 중요한 정보를 제공할 것이다. 또한, 보다 우수한 EM 특성을 가질 수 있게 하기 위해 barrier layer위에 Cu와의 접착력(adhesion)을 향상시킬 수 있는 promoter로 Al을 이용하여 얇게 증착한 후 EM축적 파괴 실험을 하여 EM에 대한 높은 저항성을 실질적으로 가질 수 있는지에 대한 실험도 병행하였다.

• Transactions on Electrical and Electronic Materials
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• 제15권6호
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• pp.315-319
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• 2014

In this paper, we investigate visible light stress instability in radio frequency (RF) sputtered a-IGZO thin film transistors (TFTs). The oxygen flow rate differs during deposition to control the concentration of oxygen vacancies, which is confirmed via RT PL. A negative shift is observed in the threshold voltage ($V_{TH}$) under illumination with/without the gate bias, and the amount of shift in $V_{TH}$ is proportional to the concentration of oxygen vacancies. This can be explained to be consistent with the ionization oxygen vacancy model where the instability in $V_{TH}$ under illumination is caused by the increase in the channel conductivity by electrons that are photo-generated from oxygen vacancies, and it is maintained after the illumination is removed due to the negative-U center properties.

• 한국전기전자재료학회논문지
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• 제22권11호
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• pp.992-998
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• 2009

We investigated the influence of organic solvents on the droplet properties of 6,13-bis (triisopropylsilylethynyl) pentacene (TIPS-pentacene), which was used for semiconductor of organic thin film transistors (OTFTs) and deposited by ink jet printing. From the result of the investigation, the conditions of a suitable solvent is that boiling point should be above $200^{\circ}C$ to reduce coffee stain and the surface tension above 32 dyn/cm to decrease the droplet size. Consequently, we selected tetralin which have a high boiling point ($207^{\circ}C$) and high surface tension (34.3 dyn/cm) as the solvent for TIPS-pentacene, and applied it to OTFTs. In fabrication process the conventional bank process employing photolithography and etching process was replaced by ink jet printed bank process, resulting in simplifying the process. Especially, polyvinylphenol was used for the bank, and the high hydrophobicity could improve the confinement of TIPS molecules inside the bank, enhancing the performance over the conventional hydrophilic polyvinylalcohol bank. The mobility was $0.18\;cm^2/Vs$, current on/off ratio $2.09{\times}10^5$, subthreshold slope 0.42 V/dec, and off state current $0.049\;pA/{\mu}m$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1336_1337
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• 2009

본 논문에서는 유기 박막 트랜지스터의 전극을 잉크젯 프린팅과 스크린 프린팅 방법을 이용하여 유기 박막 트랜지스터를 제작하였다. 전극으로 PEDOT:PSS와 Ag 잉크를 사용하였고, 게이트 절연막으로 polymethyl methacrylate (PMMA)와 poly(4-vinylphenol) (PVP)를 사용하였다. 유기물 활성층으로 pentacene을 진공 증착하였다. 잉크젯 프린팅 방법을 이용하여 제작한 유기 박막 트랜지스터는 전계이동도 (${\mu}_{FET}$) $0.068\;cm^2$/Vs, 문턱전압 ($V_{th}$) -15 V, 전류 점멸비 ($I_{on}/I_{off}$ current ratio) >$10^4$의 전기적 특성을 보였고, 스크린 인쇄 방법을 이용하여 제작한 유기 박막 트랜지스터는 전계이동도 (${\mu}_{FET}$) $0.016\;cm^2$/Vs, 문턱전압 ($V_{th}$) 6 V, 전류 점멸비 ($I_{on}/I_{off}$ current ratio) >$10^4$의 전기적 특성을 보였다. 이를 통하여 프린팅 방법을 이용한 유기 박막 트랜지스터 단일 소자 및 유기 전자 회로 제작의 가능성을 확인 하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1246_1247
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• 2009

Effects of hydrogen and oxygen additives on structural, optical, and electrical properties of ZnO films were extensively examined. ZnO films were deposited using RF sputtering by varying the gas mixing ratio of $H_2$ and $O_2$. Optical transmittances at visible region, electrical resistivities, and micro-structures of ZnO films were characterized in terms of the kind and amount of additive gases. It was observed that the material properties of ZnO films required for their use in transparent thin film transistors, such as approximately $10^3{\Omega}cm$ in resistivity and higher than 85% in transmittance, can be achieved by controlling the gas mixing ratio of $O_2/H_2$ (sccm) in the range of 2/2~2/8.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1208-1211
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• 2008

We study the amorphous In-Ga-Zn-O thin-film transistors (TFTs) properties under monochromatic illumination ($\lambda=420nm$) with different intensity. TFT off-state drain current ($I_{DS_off}$) was found to increase with the light intensity while field effect mobility ($\mu_{eff}$) is almost unchanged; only small change was observed for sub-threshold swing (S). Due to photo-generated charge trapping, a negative threshold voltage ($V_{th}$) shift is also observed. The photofield-effect analysis suggests a highly efficient UV photocurrent conversion in a-IGZO TFT. Finally, a-IGZO mid-gap density-of-states (DOS) was extracted and is more than an order lower than reported value for a-Si:H, which can explain a good switching properties of the a-IGZO TFTs.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1361-1363
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• 2005

In this paper, we report on the performance stability of solution processible OTFT devices with Au/Ti and ITO source-drain (S/D) electrodes. It appears that the contact resistance of the S/D electrode strongly affects the stability of OTFT devices. Interestingly, the devices with the Au/Ti electrode showed lower mobility than those with the ITO (S/D) devices. The field effect mobilities of the devices with the Au/Ti and ITO electrodes were 0.06, and $0.44cm^2/Vs$, respectively. However, the mobility of the device with the Au/Ti electrode was increased up to $0.26cm^2/Vs$ after 2 weeks, while the mobility of the device with ITO electrode was slightly decreased down to $0.41cm^2/Vs$. The experimental data show us that ITO could be used as the S/D electrode for low-cost OTFT devices.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1301-1305
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• 2005

The performance of OTFT with $PVP-TiO_2$ composite, as a gate insulator, is reported, including the effect of surfactant for synthesizing the composite material. According to our investigation results, it was one of critical issues to prevent the aggregation of $PVP-TiO_2$ particles during the synthesis process. From this point of view, $PVP-TiO_2$ particles were treated using Tween80, as a surfactant, and we could reduce the aggregated $PVP-TiO_2$ clusters. As a result, the OTFT with the composite insulator showed the threshold voltage of about -8.3 V and the subthreshold slope of about 1.5 V/decade, which are the optimized properties compared to those of OTFTs with bare PVP, in this study. It is thought that these characteristic improvements are originated from the increase in the dielectric constant of the PVP-based insulator by compositing with high-k particles.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1333-1336
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• 1998

Hydrogenated amorphous silicon(a-Si:H) films which were deposited by plasma enhanced chemical deposition(PECVD) have been recrystallized by the two-step rapid thermal annealing(RTA) employing the halogen lamp. The a-Si:H films evolve hydrogen explosively during the high temperature crystallzation step. In result, the recrystallized polycrystalline silicon(poly-Si) films have poor surface morphology. In order to avoid the hydrogen evolution, the films have undergone the dehydrogenation step prior to the crystallization step Before the RTA process, the active area of thin film transistors (TFT's) was patterned. The prepatterning of the a-Si:H active islands may reduce thermal damage to the glass substrate during the recrystallization. The computer generated simulation shows the heat propagation from the a-Si:H islands into the glass substrate. We have fabricated the poly-Si TFT's on the silicon wafers. The maximun ON/OFF current ratio of the device was over $10^5$.