• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.138-138
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• 2017

차세대 CMOS 소자의 지속적인 고직접화를 위해서는 높은 gate capacitance와 낮은 gate leakage current를 확보를 위한, 적절한 metal gate electrode와 high-k dielectric 물질의 개발이 필수적으로 요구된다. 특히, gate dielectric으로 적용하기 위한 다양한 high-k dielectric 물질 후보군 중에서, 높은 dielectric constant와, 낮은 leakage current, 그리고 Si과의 우수한 열적 안정성을 가지는 Zr silicates 또는 Hf silicates(ZrSiO4와 HfSiO4) 물질이 높은 관심을 받고 있으며, 이를 원자층 증착법을 통해 구현하기 위한 노력들이 있어왔다. 그러나, 현재까지 보고된 원자층 증착법을 이용한 Zr silicates 및 Hf silicates 공정의 경우, 개별적인 Zr(또는 Hf)과 Si precursor를 이용하여 ZrO2(또는 HfO2)과 SiO2를 반복적으로 증착하는 방식으로 Zr silicates 또는 Hf silicates를 형성하고 있어, 전체 공정이 매우 복잡해지는 문제점 뿐 아니라, gate dielectric 내에서 Zr과 Si의 국부적인 조성 불균일성을 야기하여, 제작된 소자의 신뢰성을 떨어뜨리는 문제점을 나타내왔다. 따라서, 본 연구에서는 이러한 문제점을 개선하기 위하여, 하나의 precursor에 Zr (또는 Hf)과 Si 원소를 동시에 가지고 있는 DNS-Zr과 DNS-Hf bimetallic precursor를 이용하여 새로운 ZrSiO4와 HfSiO4 ALD 공정을 개발하고, 그 특성을 살펴보고자 하였다. H2O와 O3을 reactant로 사용한 원자층 증착법 공정을 통하여, Zr:Si 또는 Hf:Si의 화학양론적 비율이 항상 일정한 ZrSiO4와 HfSiO4 박막을 형성할 수 있었으며, 이들의 전기적 특성 평가를 진행하였으며, dielectric constant 및 leakage current 측면에서 우수한 특성을 나타냄을 확인할 수 있었다. 이러한 결과를 바탕으로, bimetallic 전구체를 이용한 ALD 공정은 차세대 고성능 논리회로의 게이트 유전물질에 응용이 가능할 것으로 판단된다.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1185-1188
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• 2006

Pentacene thin film transistors (OTFTs) on flexible polyimide substrate using electroplated gate electrode and organic/high-k inorganic bilayer gate dielectric layer. Incorporation of thin atomic-layer deposited $HfO_2$ layer on the PVP organic gate dielectric layer reduced the gate leakage and as a result enhanced the current on/off ratio.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.445-448
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• 2006

Bias stress effect in pentacene organic thin-flim transistors with cross-linked PVA gate dielectric is analyzed. For negative gate bias stress, positive threshold voltage shift is observed. The injected charges from the gate electrode to the defect states of gate dielectric are regarded as the main origin of $V_T$ shift. The reduced bias stress effect using $SiO_2$ blocking layer confirms the assumed mechanism. It is also demonstrated that the inverter with $SiO_2$ blocking layer shows the negligible hysteresis owing to the reduced bias stress effect.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.278.1-278.1
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• 2014

Organic materials have been explored as the gate dielectric layers in thin film transistors (TFTs) of backplane devices for flexible display because of their inherent mechanical flexibility. However, those materials possess some disadvantages like low dielectric constant and thermal resistance, which might lead to high power consumption and instability. On the other hand, inorganic gate dielectrics show high dielectric constant despite their brittle property. In order to maintain advantages of both materials, it is essential to develop the alternative materials. In this work, we manufactured nanocomposite gate dielectrics composed of organic material and inorganic nanoparticle and integrated them into organic TFTs. For synthesis of nanocomposite gate dielectrics, polyimide (PI) was explored as the organic materials due to its superior thermal stability. Candidate nanoprticles (NPs) of halfnium oxide, titanium oxide and aluminium oxide were considered. In order to realize NP concentration dependent electrical characteristics, furthermore, we have synthesized the different types of nanocomposite gate dielectrics with varying ratio of each inorganic NPs. To analyze gate dielectric properties like the capacitance, metal-Insulator-metal (MIM) structures were prepared together with organic TFTs. The output and transfer characteristics of organic TFTs were monitored by using the semiconductor parameter analyzer (HP4145B), and capacitance and leakage current of MIM structures were measured by the LCR meter (B1500, Agilent). Effects of mechanical cyclic bending of 200,000 times and thermally heating at $400^{\circ}C$ for 1 hour were investigated to analyze mechanical and thermal stability of nanocomposite gate dielectrics. The results will be discussed in detail.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.491-491
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• 2011

Transparent and flexible electronic devices that are light-weight, unbreakable, low power consumption, optically transparent, and mechanical flexible possibly have great potential in new applications of digital gadgets. Potential applications include transparent displays, heads-up display, sensor, and artificial skin. Recent reports on transparent and flexible field-effect transistors (tf-FETs) have focused on improving mechanical properties, optical transmittance, and performances. Most of tf-FET devices were fabricated with transparent oxide semiconductors which mechanical flexibility is limited. And, there have been no reports of transparent and flexible all-organic tf-FETs fabricated with organic semiconductor channel, gate dielectric, gate electrode, source/drain electrode, and encapsulation for sensor applications. We present the first demonstration of transparent, flexible all-organic sensor based on multifunctional organic FETs with organic semiconductor channel, gate dielectric, and electrodes having a capability of sensing infrared (IR) radiation and mechanical strain. The key component of our device design is to integrate the poly(vinylidene fluoride-triflouroethylene) (P(VDF-TrFE) co-polymer directly into transparent and flexible OFETs as a multi-functional dielectric layer, which has both piezoelectric and pyroelectric properties. The P(VDF-TrFE) co-polumer gate dielectric has a high sensitivity to the wavelength regime over 800 nm. In particular, wavelength variations of P(VDF-TrFE) molecules coincide with wavelength range of IR radiation from human body (7000 nm ~14000 nm) so that the devices are highly sensitive with IR radiation of human body. Devices were examined by measuring IR light response at different powers. After that, we continued to measure IR response under various bending radius. AC (alternating current) gate biasing method was used to separate the response of direct pyroelectric gate dielectric and other electrical parameters such as mobility, capacitance, and contact resistance. Experiment results demonstrate that the tf-OTFT with high sensitivity to IR radiation can be applied for IR sensors.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.64.1-64.1
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• 2012

Next generation displays such as high performance LCD, AMOLED, flexible display and transparent display require specific TFT back-planes. For high performance TFT back-planes, low temperature poly silicon (LTPS), and metal-oxide semiconductors are studied. Flexible TFT backplanes require low temperature processible organic semiconductors. Not only development of active semiconducting materials but also design and synthesis of semiconductor corresponding gate dielectric materials are important issues in those display back-planes. In this study, we investigate the high heat resistant polymeric gate dielectric materials for organic TFT and inorganic TFT with good insulating properties and processing chemical resistance. We also controlled and optimized surface energy and morphology of gate dielectric layers for direct printing process with solution processible organic and inorganic semiconductors.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1771-1773
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• 2007

Surface modification of the gate dielectric has a strong influence on the performance of printed transistors. The surface modification occurs between the gate dielectric and semiconductor. The printed transistor with evaporated vanadium pentoxide ($V_2O_5$) modification exhibits a mobility of $0.2cm^2\;V^{-1}\;s{-1}$ and a subthreshold slope of 1.47 V/decade.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1932-1938
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• 2003

We have applied spectroscopic ellipsometry to investigate $high-{\kappa}$ dielectric thin films and correlate their optical properties with fabrication processes, in particular, with high temperature annealing. The use of high-k dielectrics such as $HfO_{2}$, $Ta_{2}O_{5}$, $TiO_{2}$, and $ZrO_{2}$ as the replacement for $SiO_{2}$ as the gate dielectric in CMOS devices has received much attention recently due to its high dielectric constant. From the characteristics found in the pseudo-dielectric functions or the Tauc-Lorentz dispersions, the optical properties such as optical band gap, polycrystallization, and optical density will be discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.59-59
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• 2009

The efficiency of CMOS technology has been developed in uniform rate. However, there was a limitation of reducing the thickness of Gate-oxide since the thickness of Gate Dielectric is also reduced so an amount of leakage current is grow. In order to solve this problem, the semiconductor device which has a dual gate is used widely. This paper presents a method and a necessity for making the Gate Stack of TFT. Before Using test devices to measure values, stacking $SiN_x$ on a wafer test was conducted.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2563-2564
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• 2013