• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.288-289
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• 2011

Indium Tin Oxide (ITO) is a typical highly Transparent Conductive Oxide (TCO) currently used as a transparent electrode material. Most widely used deposition method is the sputtering process for ITO film deposition because it has a high deposition rate, allows accurate control of the film thickness and easy deposition process and high electrical/optical properties. However, to apply high quality ITO thin film in a flexible microelectronic device using a plastic substrate, conventional DC magnetron sputtering (DMS) processed ITO thin film is not suitable because it needs a high temperature thermal annealing process to obtain high optical transmittance and low resistivity, while the generally plastic substrates has low glass transition temperatures. In the room temperature sputtering process, the electrical property degradation of ITO thin film is caused by negative oxygen ions effect. This high energy negative oxygen ions(about over 100eV) can be critical physical bombardment damages against the formation of the ITO thin film, and this damage does not recover in the room temperature process that does not offer thermal annealing. Hence new ITO deposition process that can provide the high electrical/optical properties of the ITO film at room temperature is needed. To solve these limitations we develop the Magnetic Field Shielded Sputtering (MFSS) system. The MFSS is based on DMS and it has the plasma limiter, which compose the permanent magnet array (Fig.1). During the ITO thin film deposition in the MFSS process, the electrons in the plasma are trapped by the magnetic field at the plasma limiters. The plasma limiter, which has a negative potential in the MFSS process, prevents to the damage by negative oxygen ions bombardment, and increases the heat(-) up effect by the Ar ions in the bulk plasma. Fig. 2. shows the electrical properties of the MFSS ITO thin film and DMS ITO thin film at room temperature. With the increase of the sputtering pressure, the resistivity of DMS ITO increases. On the other hand, the resistivity of the MFSS ITO slightly increases and becomes lower than that of the DMS ITO at all sputtering pressures. The lowest resistivity of the DMS ITO is $1.0{\times}10-3{\Omega}{\cdot}cm$ and that of the MFSS ITO is $4.5{\times}10-4{\Omega}{\cdot}cm$. This resistivity difference is caused by the carrier mobility. The carrier mobility of the MFSS ITO is 40 $cm^2/V{\cdot}s$, which is significantly higher than that of the DMS ITO (10 $cm^2/V{\cdot}s$). The low resistivity and high carrier mobility of the MFSS ITO are due to the magnetic field shielded effect. In addition, although not shown in this paper, the roughness of the MFSS ITO thin film is lower than that of the DMS ITO thin film, and TEM, XRD and XPS analysis of the MFSS ITO show the nano-crystalline structure. As a result, the MFSS process can effectively prevent to the high energy negative oxygen ions bombardment and supply activation energies by accelerating Ar ions in the plasma; therefore, high quality ITO can be deposited at room temperature.

• Journal of the Semiconductor & Display Technology
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• v.14 no.3
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• pp.33-36
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• 2015

It has increased several decades in the field of Indium Tin Oxide (ITO) transparent thin film, However, a major problem with this ITO thin film application is high cost compared with other transparent thin film materials[1]. So far, in order to overcome this disadvantage, we show that a transparent ITO/Ag/i-ZnO multilayer thin film electrode would be more cost-effective and it has not only highly transparent but also conductive properties. The aim of this research has therefore been to try and establish how ITO/Ag/i-ZnO multilayer thin film would be more effective than ITO thin film. Herein, we report the properties of ITO/Ag/i-ZnO multilayer thin film by using optical spectroscopic method and measuring sheet resistance. At a certain total thickness of thin film, sheet resistance of ITO/Ag/i-ZnO multilayer was drastically decreased than ITO layer approximately $40{\Omega}/{\Box}$ at same visible light transmittance. (minimal point $5.2{\Omega}/{\Box}$). Tendency, which shows lowly sheet resistive in a certain transmittance, has been observed, hence, it should be suitable for transparent electrode device.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.581-581
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• 2013

ITO (Indium Tin oxide)는 비화학 양론적 조성을 띄는 n-type 반도체 특성이 있으며 가시광 영역(380~780 nm)의 파장에 대한 높은 광 투과도(>85%)를 가지며 비교적 높은 전도도(${\sim}10^4/{\Omega}-cm$)를 갖고 화학적 안정성이 우수하여 투명전극 박막으로 많이 사용되어왔다. 또한, PET film은 전기절연성, 내후성이 우수하고, 85%의 투과율을 보이는 특성에 의하여 Flexible display의 기판으로 많은 연구가 진행되고 있다. 이와 같은 PET film에 ITO를 증착하여 광 투과도와 전기전도도가 우수한 Flexible display의 투명전극으로 많은 연구 개발이 이루어지고 있다. Flexible ITO 박막의 특성을 향상하기 위해서는 $200^{\circ}C$ 이상의 열처리 공정이 필요하지만, PET는 약 $200^{\circ}C$ 이상에서 열 변형이 일어나므로 열처리 공정이 어렵고 이러한 문제점을 해결하기 위해 ITO/PET film에서 PET film의 변형 없이 ITO 박막의 표면에 전자빔 형태로 조사하여 박막의 물성을 개선하는 연구가 진행되고 있다 [1]. 본 연구에서는 ITO/$SiO_2$가 증착된 PET film에 전자빔을 조사하여 ITO 박막의 물성 변화를 관찰하였고, 전자빔 에너지 변화 및 전자빔 조사 시간에 따라 ITO film의 전기적, 광학적 특성 변화를 분석하였다. 구조적 특성은 XRD (X-ray diffraction), 전기적 특성은 4-point probe, Hall measurement를 이용하였으며, 가시광영역의 광 투과도는 UV-Vis spectrometer로 측정하였다. 전기 광학적 특성 변화는 Figure of Merit (FOM) 수치로 분석하였다. 이 실험으로 PET film에 직접적인 열을 가하지 않으면서 ITO 박막의 표면에 전자빔을 조사 하여, 박막의 전기전도도 및 광 투과율, 결정성 향상 등을 관찰할 수 있었다.

• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.86-93
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• 2009

The crack formation and the resistance of ITO film on PET substrate with a thickness of 20 nm were investigated as a function of strain. The onset strain for the increase of resistance increased with increasing strain rate, suggesting the crack initiation is dependent on the strain rate. Electrical resistance increased at the strain of 1.6% at the strain rates below $10^{-4}/sec$ while it increased at ${\sim}2%$ at the strain rates above $10^{-3}/sec$. The critical strain at which the cracks were formed is close to the proportional limit. Upon loading, the initial cracks perpendicular to the tensile axis were observed and propagated the whole sample width with increasing strain. The spacing between horizontal cracks is thought to be determined by the fracture strength and the interfacial strength between ITO and PET. The crack density increased with increasing strain. However, the effect of the strain rate on the crack density was less pronounced in ITO/PET with 20 nm ITO thickness than ITO/PET with 125 nm ITO thickness, the strength of ITO film is thought to increase as the thickness on ITO film decreases. The absence of cracks on ITO film at a strain as close as 1.5% can be attributed to the compressive residual stress of ITO film which was developed during cooling after the coating process. The higher critical strain for the onset of the resistance increase and the crack initiation of ITO/PET with a thinner ITO film (20 nm) can be linked with the higher strength of the thinner ITO film.

• Korean Journal of Materials Research
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• v.16 no.8
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• pp.490-496
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• 2006

ITO monolayer and ITO/Ag/ITO multilayer thin films are prepared by D.C. magnetron sputtering method. Ag layer was inserted for applying ITO to a flexible substrate at low temperature. Carrier concentration and carrier mobility of ITO and ITO/Ag/ITO thin films were measured, the transmittance of them also was done. The amorphous phase was confirmed to be combined in addition to (400) and (440) peaks from XRD result of ITO thin film. As the substrate temperature increased, the preferred orientation of (400) appeared. From the result of application of Ag layer at room temperature, the growth of columnar structure was inhibited, and the amorphous phase formed mostly. The ITO/Ag/ITO thin film represented the transmittance of above 80% when the thickness of Ag layer was 50 ${\AA}$, and the concentration of carrier increased up to above 10 times than that of ITO thin film. Finally, since very low resistance of 3.9${\Omega}/{\square}$ was observed, the effective application of low temperature process is expected to be possible for ITO thin film.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.192-196
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• 2011

The multi-layered thin film with an ITO/Ag/ITO structure was produced on PET by using magnetron reactive sputtering method. First, 30 nm of ITO thin film was coated on PET by using normal temperature process. Then 20-52 nm of the Ag thin film was coated. Lastly, 30 nm of ITO thin film was coated on Ag layer. The sample of the 20 nm Ag thin film showed more than 70% transmission and a $2.7{\Omega}/{\Box}$ sheet resistance. When compared to the existing single-layered transparent conducting thin film, multi-layered film was found to be superior with about $5{\Omega}/{\Box}$ less sheet resistance. However, since the Ag layer became thinner, the band gap energy needs to be increased to more than 3.5 eV.

• Journal of IKEEE
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• v.20 no.2
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• pp.171-173
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• 2016

In this study, we fabricate a high efficiency heater consisting of the indium tin oxide (ITO) nanoparticle (NP)-paste and polydimethylsiloxane (PDMS) and investigate the effect of PDMS on temperature maintenance of the heater through the comparison with the PDMS-free ITO film heater. Compared to the ITO film heater, the temperature of the PDMS/ITO film heater lasts 1.5 times longer. And the power consumption of the PDMS/ITO film heater is reduced by 35%, owing to the low thermal conductivity of the PDMS layer.

• Korean Journal of Materials Research
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• v.25 no.7
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• pp.352-357
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• 2015

To research the characteristics of ITO film depending on a polarity of SiOC, specimens of ITO/SiOC/glass with metal-insulator-substrates (MIS) were prepared using a sputtering system. SiOC film with 17 sccm of oxygen flow rate became a non-polarity with low surface energy. The PL spectra of the ITO films deposited with various argon flow rates on SiOC film as non-polarity were found to lead to similar formations. However, the PL spectra of ITO deposited with various argon flow rates on SiOC with polarity were seen to have various features owing to the chemical reaction between ITO and the polar sites of SiOC. Most ITO/SiOC films non-linearly showed the Schottky contacts and current increased. But the ITO/SiOC film with a low current demonstrated an Ohmic contact.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.187-187
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• 2015

The past thirty years have seen increasingly rapid advances in the field of Indium Tin Oxide (ITO) transparent thin film.[1] However, a major problem with this ITO thin film application is high cost compared with other transparent thin film materials.[2] So far, in order to overcome this disadvantage, we show a transparent ITO/Ag/i-ZnO multilayer thin film electrode can be the solution. In comparison with using amount of ITO as a transparent conducting material, intrinsic-Zinc-Oxide (i-ZnO) based on ITO/Ag/i-ZnO multilayer thin film showed cost-effective and it has not only highly transparent but also conductive properties. The aim of this research has therefore been to try and establish how ITO/Ag/i-ZnO multilayer thin film would be more effective than ITO thin film. Herein, we report ITO/Ag/i-ZnO multilayer thin film properties by using optical spectroscopic method and measuring sheet resistance. At a certain total thickness of thin film, sheet resistance of ITO/Ag/i-ZnO multilayer was drastically decreased than ITO layer approximately $40{\Omega}/{\square}$ at same visible light transmittance.(minimal point $5.2{\Omega}/{\square}$). Tendency, which shows lowly sheet resistive in a certain transmittance, has been observed, hence, it should be suitable for transparent electrode device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.741-746
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• 2009

Compare to conventional Indium Tin Oxide (ITO) film deposition methods, cesium assisted sputtering method has been shown superior electrical, mechanical, and optical film properties. However, it is not easy to use cesium assisted sputtering method since ITO film properties are very sensitive to Cesium assisted equipment condition but their mechanism is not yet clearly defined physically or mathematically. Therefore, to optimize deposited ITO film characteristics, development of accurate and reliable process model is essential. For this, in this work, we developed ITO film deposition process model using neural networks and design of experiment (DOE). Developed model prediction results are compared with conventional statistical regression model and developed neural process model has been shown superior prediction results on modeling of ITO film thickness, sheet resistance, and transmittance characteristics.