• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.211.1-211.1
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• 2015

최근 용액 공정을 이용한 산화물 반도체에 대한 연구가 활발히 진행되고 있다. 넓은 밴드갭을 가지고 있는 산화물 반도체는 높은 투과율을 가지고 있어 투명 디스플레이에 적용이 가능하다. 기존의 박막 진공증착 방법은 진공상태를 유지하기 위한 장비의 가격이 비싸며, 대면적의 어려움, 높은 생산단가 등으로 생산율이 높지 않다. 하지만 용액 공정을 이용하면 대기압에서 증착이 가능하고 대면적화가 가능하다. 그리고 각각의 조성비를 조절하는 것이 가능하다. 이러한 장점에도 불구하고, 소자의 신뢰성이나 저온공정은 중요한 이슈이다. Instability는 threshold voltage (Vth)의 shift 및 on/off switching의 신뢰성과 관련된 parameter이다. 용액은 소자의 전기적 특성을 열화 시키는 수분 과 탄소계열의 불순물을 다량 포함 하고 있어 고품질의 박막을 형성하기 위해서는 고온의 열처리가 필요하다. 기존의 열처리는 고온에서 장시간 이루어지기 때문에 유리나 플라스틱, 종이 기판의 소자에서는 불가능하지만 $100^{\circ}C$ 이하의 저온 공정인 microwave를 이용하면 유리, 플라스틱, 종이 기판에서도 적용이 가능하다. 본 연구에서는 산화물 반도체 중에서 InGaZnO (IGZO)를 용액 공정으로 제작한 juctionless thin-film transistor를 제작하여 기존의 열처리를 이용하여 처리한 소자와 microwave를 이용해서 열처리한 소자의 전기적 특성을 한 달 동안 관찰 하였다. 또한 In:Zn의 비율을 고정한 후 Ga의 비율을 달리하여 특성을 비교하였다. 먼저 p-type bulk silicon 위에 SiO2 산화막이 100 nm 증착된 기판에 RCA 클리닝을 진행 하였고, solution InGaZnO 용액을 spin coating 방식으로 증착하였다. Coating 후에, solvent와 수분을 제거하기 위해서 $180^{\circ}C$에서 10분 동안 baking공정을 하였다. 이후 furnace열처리와 microwave열처리를 비교하기 위해 post-deposition-annealing (PDA)으로 furnace N2 분위기에서 $600^{\circ}C$에서 30분, microwave를 1800 W로 2분 동안 각각의 샘플에 진행하였다. 또한, HP 4156B semiconductor parameter analyzer를 이용하여 제작된 TFT의 transfer curve를 측정하였다. 그 결과, microwave 열처리한 소자의 경우 기존의 furnace 열처리 소자와 비교하여 높은 mobility, 낮은 hysteresis 값을 나타내었으며, 1달간 소자의 특성을 관찰하였을 때 microwave 열처리한 소자의 경우 전기적 특성이 거의 변하지 않는 것을 확인하였다. 따라서 향후 용액공정, 저온공정을 요구하는 소자 공정에 있어 열처리방법으로 microwave를 이용한 활용이 기대된다.

• 한국재료학회지
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• 제30권4호
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• pp.211-216
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• 2020

Amorphous In-Ga-Zn-O (a-IGZO) thin film transistors, because of their relatively low mobility, have limits in attempts to fulfill high-end specifications for display backplanes. In-Zn-O (IZO) is a promising semiconductor material for high mobility device applications with excellent transparency to visible light region and low temperature process capability. In this paper, the effects of working pressure on the physical and electrical properties of IZO films and thin film transistors are investigated. The working pressure is modulated from 2 mTorr to 5 mTorr, whereas the other process conditions are fixed. As the working pressure increases, the extracted optical band gap of IZO films gradually decreases. Absorption coefficient spectra indicate that subgap states increase at high working pressure. Furthermore, IZO film fabricated at low working pressure shows smoother surface morphology. As a result, IZO thin film transistors with optimum conditions exhibit excellent switching characteristics with high mobility (≥ 30㎠/Vs) and large on/off ratio.

• 센서학회지
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• 제28권2호
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• pp.133-138
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• 2019

The a-InGaZnO (a-IGZO) thin film transistor (TFT) has the advantages of larger mobility than that of amorphous silicon TFTs, acceptable reliability and uniformity over a large area, and low process cost. A capacitive-type touch sensor was studied with an a-IGZO TFT that can be used on the front side of a display due to its transparency. A capacitive sensor detects changes of capacitance between the surface of the finger and the sensor electrode. The capacitance varies according to the distance between the sensor plate and the touching or non-touching of the sensing electrode. A capacitive touch sensor using only one a-IGZO TFT was developed with the reduction of two bus lines, which made it easy to reduce the pixel pitch. The proposed sensor circuit maintained the amplification performance, which was investigated for various drive conditions.

• ETRI Journal
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• 제28권6호
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• pp.787-789
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• 2006

In this letter, we report that vertically well-aligned ZnO nanowires were grown on GaN epilayers and c-plane sapphire via a vapor-liquid-solid process by introducing a 3 nm Au thin film as a catalyst. In our experiments, epitaxially grown ZnO nanowires on Au-coated GaN were vertically well-aligned, while nanowires normally tilted from the surface when grown on Au-coated c-$Al_2O_3$ substrates. However, pre-growth annealing of the Au thin layer on c-$Al_2O_3$ resulted in the growth of well-aligned nanowires in a normal surface direction. High-resolution transmission electron microscopy measurements showed that the grown nanowires have a hexagonal c-axis orientation with a single-crystalline structure.

• Current Photovoltaic Research
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• 제3권2호
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• pp.54-60
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• 2015

ZnSnO thin films were deposited by atomic layer deposition (ALD) process using diethyl zinc ($Zn(C_2H_5)_2$) and tetrakis (dimethylamino) tin ($Sn(C_2H_6N)_4$) as metal precursors and water vapor as a reactant. ALD process has several advantages over other deposition methods such as precise thickness control, good conformality, and good uniformity for large area. The composition of ZnSnO thin films was controlled by varying the ratio of ZnO and $SnO_2$ ALD cycles. The ALD ZnSnO film was an amorphous state. The band gap of ZnSnO thin films increased as the Sn content increased. The CIGS solar cell using ZnSnO buffer layer showed about 18% energy conversion efficiency. With such a high efficiency with the ALD ZnSnO buffer and no light soaking effect, AlD ZnSnO buffer mighty be a good candidate to replace Zn(S,O) buffer in CIGSsolar cells.

• 한국전기전자재료학회논문지
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• 제26권4호
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• pp.304-308
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• 2013

For the application to the window layer of $Cu(In,Ga)Se_2$(CIGS) solar cell, zinc oxide(ZnO) thin film was deposited at various temperatures by in-line pulsed DC sputtering. From the structural, optical, and electrical investigation and analysis, it was possible to obtain the lower thickness, the lower resistivity, and the higher transmittance at a higher process temperature. The energy band gap of ZnO was calculated using the transmittance data and was analyzed in terms of the dependency on temperature. From the X-ray diffraction(XRD) results, it was possible to conclude that a dominant peak was found about $34.2{\sim}34.6^{\circ}$(111) and crystallinity was obtained at a temperature above $150^{\circ}C$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.256-256
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• 2012

Oxide semiconductors such as zinc tin oxide (ZTO) or indium gallium zinc oxide (IGZO) have attracted a lot of research interest owing to their high potential for application as thin film transistors (TFTs) [1,2]. However, the instability of oxide TFTs remains as an obstacle to overcome for practical applications to electronic devices. Several studies have reported that the electrical characteristics of ZnO-based transistors are very sensitive to oxygen, hydrogen, and water [3,4,5]. To improve the reliability issue for the amorphous InGaZnO (a-IGZO) thin-film transistor, back channel passivation layer is essential for the long term bias stability. In this study, we investigated the instability of amorphous indium-gallium-zinc-oxide (IGZO) thin film transistors (TFTs) by the back channel contaminations. The effect of back channel contaminations (humidity or oxygen) on oxide transistor is of importance because it might affect the transistor performance. To remove this environmental condition, we performed vacuum seasoning before the deposition of hybrid passivation layer and acquired improved stability. It was found that vacuum seasoning can remove the back channel contamination if a-IGZO film. Therefore, to achieve highly stable oxide TFTs we suggest that adsorbed chemical gas molecules have to be eliminated from the back-channel prior to forming the passivation layers.

• 한국정보통신학회논문지
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• 제16권3호
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• pp.558-564
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• 2012

Sol-gel 법으로 Eagle 2000 유리 기판 위에 Ga 도핑 농도와 열처리 온도에 따른 GZO 박막을 제작하여, 전기적 및 광학적 특성을 조사하였다. 1 mol% Ga 이 도핑되고 $600^{\circ}C$에서 열처리한 GZO 박막에서 가장 우수한 (002) 배향성이 관찰되었다. Hall 측정 결과, Ga 도핑 농도가 증가함에 따라 segregation 효과로 인한 캐리어 농도의 감소와 비저항 값의 증가가 관찰되었다. 1 mol% Ga 이 도핑되고 $600^{\circ}C$에서 열처리한 GZO 박막에서 가장 큰 캐리어 농도($9.13{\times}10^{18}cm^{-3}$)와 가장 낮은 비저항 ($0.87{\Omega}cm$) 값을 나타내었다. 모든 박막은 가시광 영역에서 약 80 % 이상의 투과율을 보였으며, Ga 농도가 1 에서 4 mol% 로 증가함에 따라 에너지 밴드 갭이 좁아지는 Burstein-Moss 효과가 관찰되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1277_1278
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• 2009

Amorphous oxide semiconductor $InGaZnO_4$(IGZO) is a very promising candidate of channel layer in transparent thin film trasisitor(TTFT) because of its high mobility and high transparency in visible light region. Amorphous IGZO films were deposited at room temperature on a fused silica substrate using pulsed laser deposition method. In-situ post annealing was carried out at 150-450C right after film deposition. The $O_2$ partial pressures during the deposition and the post annealing was fixed to 10mTorr. The electron transport properties of the amorphous IGZO films were improved by thermal annealing. The temperature range in which the improvement of the electrical properties, was 150C~300C.

• 한국전기전자재료학회논문지
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• 제29권1호
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• pp.1-5
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• 2016

The ultimate aims of display market is transparent or flexible. Researches have been carried out for various applications. It has been possible to reduced the process steps and get good electrical properties for semiconductors with large optical bandgaps. Oxide semiconductors have been established as one of the leading and promising technology for next generation display panels. In this paper, alternative treatment processes have been tried for oxide semiconductors of thin film transistors to increase the electrical properties of the thin film transistors and to investigate the mechanisms. There exist a various oxide semiconductors. Here, we focused on InGaZnO, ZnO and InSnZnO which are commercialized or researched actively.