• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.84-84
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• 2010

In this study, we report on the novel lithographic patterning method to fabricate organic-semiconductor devices based on photo and e-beam lithography with well-known silicon technology. The method is applied to fabricate pentacene-based organic field effect transistors. Owing to their solubility, sub-micron sized patterning of P3HT and PEDOT has been well established via micromolding in capillaries (MIMIC) and inkjet printing techniques. Since the thermally deposited pentacene cannot be dissolved in solvents, other approach was done to fabricate pentacene FETs with a very short channel length (~30nm), or in-plane orientation of pentacene molecules by using nanometer-scale periodic groove patterns as an alignment layer for high-performance pentacene devices. Here, we introduce the atomic layer deposition of $Al_2O_3$ film on pentacene as a passivation layer. $Al_2O_3$ passivation layer on OTFTs has some advantages in preventing the penetration of water and oxygen and obtaining the long-term stability of electrical properties. AZ5214 and ma N-2402 were used as a photo and e-beam resist, respectively. A few micrometer sized lithography patterns were transferred by wet and dry etching processes. Finally, we fabricated sub-micron sized pentacene FETs and measured their electrical characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.224-227
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• 1995

The micro-patterning by a Bow energy FIB whish has been conventionally utilized far mask-repairing was investigated. Amorphous Se$\_$75/Gee$\_$25/ resist irradiated by 9[keV]-defocused Ga$\^$+/ ion beam(∼10$\^$15/[ions/$\textrm{cm}^2$]) resulted in increasing the optical absorption, which was also observed also in the film exposed by an optical dose of 4.5${\times}$10$\^$20/[photons/$\textrm{cm}^2$]. The ∼0.3[eV] edge shift for ion-irradiated film was about twice to that obtained for photo-exposed. These large shift could be estimated as due to an increase in disorder from the decrease in the sloop of the Urbach tail. For Ga$\^$+/ FIB irradiation with a relatively low energy, 30[keV] and above the amount of dose of 1.4${\times}$10$\^$16/[ions/$\textrm{cm}^2$], the irradiated region in a-Se$\_$75/Ge$\_$25/ resist was perfectly etched in acid solution for 10[sec], which is relatively a short development time. A contrast was about 2.5. In spite of the relatively low incident energy,∼0.225[$\mu\textrm{m}$] pattern was clearly obtained by the irradiation of a dose 6.5${\times}$10$\^$16/[ions/$\textrm{cm}^2$] and a scan diameter 0.2[$\mu\textrm{m}$], from which excellent results were expected fur incident energies above 50[keV] which was conventionally used in FIBL.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.617-620
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• 1999

In this study, the polarization e(fecal and the birefringence effect of amorphous germanium (a-Ge) thin films were investigated by using linearly polarized He-Ne laser beam. The a-7e thin films were deposited on the quarts substrate by plasma enhanced chemical vapor deposition (PECVD) and thermal vacuum evaporation In order to obtain the optimum grating arrays, inorganci resists such as Si$_3$N$_4$ and a-Se$_{75}$ Ge$_{25}$ , were prepared with the optimized thickness by Monte Carlo (MC) simulation. As the results of MC simulation, the thickness ofa-Se$_{75}$ Ge$_{25}$ resist was determined with Z$_{min}$ of 360$\AA$ . The resists were exposed to Ga$^{+}$-FIB with accelerating energies of 50 keV, developed by wet etching, and a-Ge thin film was etched by reactive ion-etching (RIE). Finally, we were obtained grating arrays which grating width and linewidth are 0.8${\mu}{\textrm}{m}$, respectively and we studied the polarization and birefringence effect in transmission grating array made of high refractive amorphous material, and the applicability as waveplates and polarizers in optical device.e.e.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1253-1256
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• 2005

We have developed an electron lithography method, Electron Emission Lithography (EEL), which is capable of printing integrated circuits with an exposure time of only a few seconds. The basic design of the mask, manufactured by standard MIM technology, will be discussed. Patterns printed into e-beam resist by a 1:1 projection system show the applicability of the mask for lithography purposes. The minimum feature size projected so far is 10 um in a system capable of 100 m resolution. Further improvements in resolution to 50 nm are possible.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.96-96
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• 2011

ZnO는 실온에서 3.37 eV의 큰 밴드갭 에너지와 60 meV의 높은 exciton binding energy를 가지고 있어 광소자를 만드는데 큰 관심을 얻고 있다. 또한 최근에는 ZnO를 기반으로 한 동종접합 전광소자를 만드는데 성공하였다. 그러나 소자의 성능을 높이기 위해 여러 가지 개선할 사항이 있다. 그 중에 하나는 캐리어를 잘 주입 시키기 위한 금속-반도체 접합을 구현하는 것이다. 이러한 문제를 개선하기 위해서는 ZnO 기반으로 한 낮은 비저항을 가진 소자가 필요하다. 일반적으로 n-type ZnO Ohmic 접합에서 쓰이는 금속은 Ti/Au, Ta/Au, Al/Au 등이 있다. 실험방법은 c-plane 사파이어 기판 위에 펄스 레이저 증착 방법으로 3시간 동안 $500^{\circ}C$ 환경에서 ZnO 박막을 성장하고, 표면을 고르게 하기 위해 $1000^{\circ}C$에서 1분 동안 열처리를 진행하였다. 샘플 위에 photo-resist 코팅을 한 다음 transfer length method(TLM)를 이용하기 위해 포토리소그래피 장비를 통하여 샘플을 노광하였다. 그 위에 Ti/Au (30 nm/80 nm)를 E-beam/thermal evaporation으로 증착 하였다. 이는 일반적인 반도체 공정과 Lift-off방식을 이용하여 패터닝 하였다. 샘플을 열처리하는 것은 금속과 반도체의 접촉 접착과 전기적인 성질을 개선하고 응력과 계면 결함을 감소시키기 때문에 샘플을 100, 200, 300, 400, $500^{\circ}C$에서 각각 열처리하였다. 저항을 구하기 위해 각각 열처리된 샘플과 as-deposited의 전류, 전압 특성을 측정하고, 이러한 실험 방법으로 n-type ZnO의 Ohmic 접합을 구현하는 것이 목표이다.

• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.63-69
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• 2011

In this study, we report on the novel lithographic patterning method to fabricate organic thin film field effect transistors (OTFTs) based on photo and e-beam lithography with well-known silicon technology. The method is applied to fabricate pentacene-based organic field effect transistors. Owing to their solubility, sub-micron sized patterning of P3HT and PEDOT has been well established via micromolding in capillaries and inkjet printing techniques. Since the thermally deposited pentacene cannot be dissolved in solvents, other approach was done to fabricate pentacene FETs with a very short channel length (~30 nm), or in-plane orientation of pentacene molecules by using nanometer-scale periodic groove patterns as an alignment layer for high-performance pentacene devices. Here, we introduce $Al_2O_3$ film grown via atomic layer deposition method onto pentacene as a passivation layer. $Al_2O_3$ passivation layer on OTFTs has some advantages in preventing the penetration of water and oxygen and obtaining the long-term stability of electrical properties. AZ5214 and ma N-2402 were used as a photo and e-beam resist, respectively. A few micrometer sized lithography patterns were transferred by wet and dry etching processes. Finally, we fabricated micron sized pentacene FETs and measured their electrical characteristics.

• Journal of the Korean Vacuum Society
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• v.15 no.6
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• pp.637-641
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• 2006

We present the DC and RF characteristics of 100 nm gate length InGaAs/InAlAs/GaAs metamorphic high electron mobility transistors (MHEMTs). We fabricated the T-gate with 100 nm foot print by using a positive resist ZEP520/P (MMA-MAA)/PMMA trilayer by double exposure method. The fabricated 100 nm MHEMT with a $70\;{\mu}m$ unit gate width and two fingers were characterized through do and rf measurements. The maximum drain current density of 465 mA/mm and extrinsic transconductance $(g_m)$ of 844 mS/mm were obtained with our devices. From rf measurements, we obtained the current gain cut-off frequency $(f_T)$ of 192 GHz, and maximum oscillation frequency $(f_{max})$ 310 GHz.

• Structural Engineering and Mechanics
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• v.39 no.6
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• pp.833-847
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• 2011

We have developed a lightweight aggregate (LWA) concrete made by expanding fine sediments dredged from the Shihmen Reservoir (Taiwan) with high heat. In this study, the performance of the concrete and of prestressed concrete beams made of the sedimentary LWA were tested and compared with those made of normal-weight concrete (NC). The test results show that the lightweight concrete (LWAC) exhibited comparable time-dependent properties (i.e., compressive strength, elastic modulus, drying shrinkage, and creep) as compared with the NC samples. In addition, the LWAC beams exhibited a smaller percentage of prestress loss compared with the NC beams. Moreover, on average, the LWAC beams could resist loading up to 96% of that of the NC beams, and the experimental strengths were greater than the nominal strengths calculated by the ACI Code method. This investigation thus established that sedimentary LWA can be recommended for structural concrete applications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.19-24
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• 2004

In this paper, we have demonstrated the fabrication of a 70 nm foot print of the T-gate by using a positive resist ZEP520/P(MMA-MAA)/PMMA trilayer by double exposure method without a thin dielectric supporting layer on the substrate. The device performance was characterized by DC and RF measurement. The fabricated 70 nm InGaAs/InAlAs MHEMTS with 70 ${\mu}{\textrm}{m}$ unit gate width and 2 fingers showed good DC and RF characteristics of Idss, max =228.6 mA/mm, gm =645 mS/mm, and fT =255 GHz, respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.71-71
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• 2003

Hot embossing has been widely accepted as an alternative to photolithography in generating patterns on polymeric substrates. The optimization of embossing process should be accomplished based on polymer substrate materials. In this paper, the effect of polymer substrates on nano scale hot embossing process was studied. Silicon molds with nano size patterns were fabricated by e-beam direct writing. Molds were coated with self-assembled monolayer (SAM) of (1, 1, 2.2H -perfluorooctyl)-trichlorosilane to reduce the stiction between mold and substrates. For an embossing, pressure of 55, 75 bur, embossing time of 5 min and temperature of above transition temperature were peformed. Polymethylmethacrylates (PMMA) with different molecular weights of 450,000 and 950,000, MR-I 8010 polymer (Micro Resist Technology) and polyaliphatic imide copolymer were applied for hot embossing process development in nano size. These polymers were spun coated on the Si wafer with the thickness between 150 and 200 nm. The nano size patterns obtained after hot embossing were observed and compared based on the polymer properties by scanning electron microscopy (SEM). The imprinting uniformity dependent on the Pattern density and size was investigated. Four polymers have been evaluated for the nanoimprint By optimizing the process parameters, the four polymers lead to uniform imprint and good pattern profiles. A reduction in the friction for smooth surfaces during demoulding is possible by polymer selection.