• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.151-151
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• 2009

Recently, there has been increasing interest in amorphous oxide semiconductors to find alternative materials for an amorphous silicon or organic semiconductor layer as a channel in thin film transistors(TFTs) for transparent electronic devices owing to their high mobility and low photo-sensitivity. The fabriction of amorphous oxide-based TFTs at room temperature on plastic substrates is a key technology to realize transparent flexible electronics. Amorphous oxides allows for controllable conductivity, which permits it to be used both as a transparent semiconductor or conductor, and so to be used both as active and source/drain layers in TFTs. One of the materials that is being responsible for this revolution in the electronics is indium-zinc-tin oxide(IZTO). Since this is relatively new material, it is important to study the properties of room-temperature deposited IZTO thin films and exploration in a possible integration of the material in flexible TFT devices. In this research, we deposited IZTO thin films on polyethylene naphthalate substrate at room temperature by using magnetron sputtering system and investigated their properties. Furthermore, we revealed the fabrication and characteristics of top-gate-type transparent TFTs with IZTO layers, seen in Fig. 1. The experimental results show that by varying the oxygen flow rate during deposition, it can be prepared the IZTO thin films of two-types; One a conductive film that exhibits a resistivity of $2\times10^{-4}$ ohm${\cdot}$cm; the other, semiconductor film with a resistivity of 9 ohm${\cdot}$cm. The TFT devices with IZTO layers are optically transparent in visible region and operate in enhancement mode. The threshold voltage, field effect mobility, on-off current ratio, and sub-threshold slope of the TFT are -0.5 V, $7.2\;cm^2/Vs$, $\sim10^7$ and 0.2 V/decade, respectively. These results will contribute to applications of select TFT to transparent flexible electronics.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1273-1276
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• 2007

We provide a newly developed dry etching process for the fabrication of ZnO-based oxide TFTs. The etching characteristics of ZnO (active layer) and $Al_2O_3$ (gate insulator) thin films were systematically investigated when the etching gas mixtures and their mixing ratios were varied in the heliconplasma etching system.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.222-225
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• 2008

We proposed the dry etching process recipe for the fabrication of In-Ga-Zn-O (IGZO)-based oxide TFTs, in which the etching behaviors of IGZO films were systematically investigated when the etching gas mixtures and their mixing ratios were varied. Good device characteristics of the fabricated TFT were successfully confirmed.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1453-1456
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• 2009

Transparent sol-gel hybrid dielectric material (hybrimer) coating films were fabricated by spin coating and photo or thermal curing of sol-gel derived oligosiloxane resins. Hybrimer coating films are suitable as the passivation layer of TFT in AMLCD due to low dielectric constant, small loss tangent, low leakage current density, high transmittance and thermal stability.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.330-332
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• 2009

Highly stable bottom gate thin film transistors(TFTs) with a zinc indium tin oxide(Zn-In-Sn-O:ZITO) channel layer have been fabricated by rf-magnetron co-sputtering using a indium tin oxide(ITO:90/10), a tin oxide and a zinc oxide targets. The ZITO TFT (W/L=$40{\mu}m/20{\mu}m$) has a mobility of 24.6 $cm^2$/V.s, a subthreshold swing of 0.12V/dec., a turn-on voltage of -0.4V and an on/off ratio of >$10^9$. When gate field of $1.8{\times}10^5$ V/cm was applied with source-drain current of $3{\mu}A$ at $60^{\circ}C$, the threshold voltage shift was ~0.18 V after 135 hours. We fabricated AM-OLED driven by highly stable bottom gate Zn-In-Sn-O TFT array.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.23.1-23.1
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• 2009

Transparent thin film transistor(TTFT)는 기존의 디스플레이가 가지고 있는 공간적, 시각적 제약을 해소하는 것이 가능하며, 이는 디스플레이 산업 및 기술이 지향하는 대면적, 저가격, 공정의 단순함을 해결해 줄 수 있기 때문에 최근 TTFT에 관한 연구가 급증하고 있다. 산화물 기반의 TFT는 유리, 금속, 플라스틱 등등 그 기판 종류에 상관없이 균일한 제작이 가능하며, 상온 및 저온에서 대면적으로 제작 가능하고, 저렴한 비용으로 제작 가능하다는 장점 때문에 최근 산화물을 기반으로 하는 TFT 연구가 많이 이루어지고 있다. 현재 TTFT 물질로 많이 연구되고 있는 산화물은 ZnO(3.4 eV)나 $InO_x$(3.6 eV), $GaO_x$(4.9 eV), $SnO_x$(3.7 eV)등의 물질과 각각의 조합으로 구성된 재료들이 주로 사용되고 있다. 가장 많은 연구가 이루어진 ZnO 기반의 TFT는 mobility와 switching 속도에서 우수한 특성을 보이나, amorphous ZnO 기반의 TFT의 경우 소자의 안정성이 떨어지는 것으로 보고되고 있다. 따라서 본 연구에서는 ZnO 보다 넓은 bandgap energy를 가질 수 있으며, n-type 특성을 보이고, amorphous 구조로 제작 가능한 IGZO 물질을 사용하여 RF magnetron sputtering 방법으로 박막 증착 온도의 변화를 주어 증착하였고, 증착된 IGZO 박막의 열처리를 통해 이에 따른 특성 변화를 분석하였다. Field emission scanning electron microscope(FESEM)와 surface profiler를 이용하여 IGZO 박막의 표면의 형상과 두께를 확인하였으며, x-ray diffraction(XRD) 분석을 통해 박막의 결정학적 특성을 관찰하였다. TTFT 물질로서 IGZO 박막의 적합성 여부를 확인하기 위하여 TFT를 만든 후 I-V를 측정하였으며, UV-vis를 이용하여 IGZO 박막의 투과율을 분석하여 TTFT로의 응용 가능성을 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.10-10
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• 2009

We have fabricated transparent and flexible thin film transistor(TFT) on polyethylene terephthalate(PET) substrate using Zinc Oxide (ZnO) and Indium Tin Oxide (ITO) film as active layer and electrode. The transfer printing method was used for printing the device layer on target plastic substrate at room temperature. This approach have an advantage to separate the high temperature annealing process to improve the electrical properties of ZnO TFT from the device process on plastic substrate. The resulting devices on plastic substrate presented mechanical and electrical properties similar with those on rigid substrate.

• ETRI Journal
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• v.35 no.4
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• pp.610-616
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• 2013

This paper proposes a transparent logic circuit for radio frequency identification (RFID) tags in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) technology. The RFID logic circuit generates 16-bit code programmed in read-only memory. All circuits are implemented in a pseudo-CMOS logic style using transparent a-IGZO TFTs. The transmittance degradation due to the transparent RFID logic chip is 2.5% to 8% in a 300-nm to 800-nm wavelength. The RFID logic chip generates Manchester-encoded 16-bit data with a 3.2-kHz clock frequency and consumes 170 ${\mu}W$ at $V_{DD}=6$ V. It employs 222 transistors and occupies a chip area of 5.85 $mm^2$.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.318-321
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• 2009

We have studied transparent top gate Al-Zn-Sn-O (AZTO) TFTs with an $Al_2O_3$ protective layer (PL) on an active layer. We also fabricated a transparent 2.5 inch QCIF+AMOLED display panel using the AZTO TFT back-plane. The AZTO active layers were deposited by RF magnetron sputtering at room temperature and the PL was deposited by ALD with two different processes. The mobility and subthreshold slope were superior in the cases of the vacuum annealing and the oxygen plasma PL compared to the $O_2$ annealing and the water vapor PL, however, the bias stability was excellent for the TFTs of the $O_2$ annealing and the water vapor PL.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.1
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• pp.26-29
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• 2006

Transparent ZnO thin films were prepared by KrF pulsed laser deposition (PLD) technique and applied to a bottom-gate type thin film transistor device as an active channel layer. A high conductive crystalline Si substrate was used as an metal-like bottom gate and SiN insulating layer was then deposited by LPCVD(low pressure chemical vapour deposition). An aluminum layer was then vacuum evaporated and patterned to form a source/drain metal contact. Oxygen partial pressure and substrate temperature were varied during the ZnO PLD deposition process and their influence on the thin film properties were investigated by X-ray diffraction(XRD) and Hall-van der Pauw method. Optical transparency of the ZnO thin film was analyzed by UV-visible phometer. The resulting ZnO-TFT devices showed an on-off ration of $10^6$ and field effect mobility of 2.4-6.1 $cm^2/V{\cdot}s$.